By John R. Levine, Margaret Levine Young

Using the Internet is exciting. But sometimes things get so fouled up that you want to push your computer out the window and go back to the communication methods our ancestors used, like newspapers, telephones, and smoke signals. Don’t give up just yet.

My PC takes forever to boot up, and pop-up ads took over the screen

Slow start-up, sluggish operation, and annoying pop-ups all suggest that your computer is infested with malware, sneaky programs that do bad things to your computer, including spyware (which arrives by way of your web browser), viruses (which arrive by email), and worms (which arrive all by themselves). A full-scale war is being waged in cyberspace for control of the world’s PCs, and your computer is likely a casualty.

Make sure that you have downloaded the latest improvements to your Windows operating system, and ensure that your virus checker and your spyware removers are up-to-date. And, if you still use Internet Explorer to browse the web, consider trying a different browser, such as Firefox, Chrome, or Safari.

Check out these antispyware programs:

For all three programs, download, install, and run them, and be sure to download updates regularly.

The nuclear option

If you have installed and run antivirus and antispyware programs and you still have problems, it may be too late for Band-Aid remedies. Your computer may be so thoroughly infested that you have no choice but to blow everything away and start over.

Before you reinstall Windows, you must install a firewall to protect your computer. Most distributed versions of Windows are so insecure that you simply cannot install the program and all its security updates before you’re reinfected with viruses and worms. (Installing and updating Windows and your application programs take a couple of hours. Infection takes perhaps ten seconds.) Even if you have only one computer, the $30 you spend for a router is well worth it.

Before you reinstall Windows, be sure to make a copy of all your files. If you haven’t been backing up regularly, make two copies, just to be safe. Back up at least one copy to more reliable CD-Rs or DVD-Rs rather than to rewritable media. Make sure that you have the installation CD or DVDs and all registration codes, license codes, and key codes for all applications you use.

If you want to reinstall Windows, you need the original CDs that came with your computer or a new copy of Windows 7 or 8. Put the Windows CD or DVD in your CD or DVD drive and reboot. Follow the instructions to the spot where it asks whether you want to rewrite or destroy all information on your hard drive. To find this spot, you may need to select advanced options. Take a deep breath and answer Yes and then Yes again to all warnings indicating that all your files will be erased. They will ― that’s why we have you back them up ― but they’ll erase the worms, too.

When the reinstallation of Windows is complete, follow the onscreen instruction to reenter your Internet settings. Then immediately click the Start button and choose All Programs→Windows Update and download all suggested updates to Windows, which takes quite a while. Load your antivirus and antispyware software and apply their latest updates. Then reinstall all your applications. Yes, this process is a real pain.

Next, place your data backup CD in the CD drive and have your antivirus program scan it. Don’t reinstall all your data files at first; just the ones you need to use. If you made two copies, keep them in two different places ― preferably, in two different buildings.

Finally, create separate, password-protected accounts for everyone who will use the computer, and make them all Limited rather than Administrator accounts unless they have a good reason to be installing their own programs. Have a talk with everyone about the risks of free downloads and online game sites. Suggest that, in case you have to repeat this process, their use of your computer will be terminated. This isn’t the kind of problem you want to keep dealing with, as you have no doubt concluded if you just had to rebuild your system.

The thermonuclear option

Because you can buy a reasonable computer for less than $300 these days and you can use the same printer and screen (if your computer isn’t a laptop) you have now, sometimes if you’ve had your old computer for a while, it’s easier to buy a new computer and start over.

The nice people at the computer store should be able to help you extract your files from your old, messed-up computer, perhaps for a modest extra charge, and install them on a new one. Even if the new computer is all configured and updated at the store, which it should be, you still should get a router to deter future hostile invasions.

The switcheroo

Plan B is to consider buying an Apple Macintosh computer or a tablet computer running the Google Android operating system, even if only for your email and web surfing. Currently, no serious online threats exist for Apple’s Mac OS X and few for Android. This situation could change, but at least Apple and Google have a head start over the hackers, rather than the other way around for Microsoft.

You should still keep your Mac’s or Android’s operating system up-to-date and rebuild your PC if you still plan to use it. If you need certain programs for the workplace, look for Mac or Android equivalents. If you have a Mac, you can also check out Boot Camp, which lets you run your Windows system and programs on your Mac.

You may also consider Ubuntu, a free system based on the open source Linux system. You can download Ubuntu for free, burn a CD, and then load it on your former Windows computer. It runs Firefox, Chrome, and Thunderbird just like any other computer, and has free LibreOffice, which does pretty much everything that Microsoft Word, PowerPoint, and Excel do. Oh, did we mention that it’s free?

I can’t send large email attachments

Some Internet service providers and some system administrators limit the size of files you can send or receive by using their mail servers. In the case of problems where you work, the solution may be as simple as talking to the person in charge of your Internet access and asking for the limit to be changed. Your ISP might not be as accommodating.

There are other ways to move giant files from point A to point B.

One great method is to use a file transfer website, such as WeTransfer, Dropbox, or Microsoft’s OneDrive. Using your web browser, go to wetransfer.com, upload the file, and enter at least one email address to notify about the file. WeTransfer sends messages to those addresses with instructions to click a link to download the file. After about two weeks, it deletes the file from its server. OneDrive allows up to 15 GB of storage for free, more if you pay for it. It uses the same login as Hotmail, so if you have a Hotmail or Outlook.com address, you already have a OneDrive account.

Another method is to open an account on a webmail provider that handles large attachments. Google Gmail allows attachments of as much as 25MB, Yahoo! Mail allows 10MB for the free version and 25MB for its paid Plus version, and Outlook.com and Hotmail allow 25MB. The process of attaching a file to a message increases its size by about 20 percent, so the maximum file size is smaller than the maximum attachment size. You can send even larger attachments to Outlook.com and Hotmail addresses, but it will detach them and put the files in OneDrive.

For local file transfers, sneakernet (a system of transferring files by walking them from one computer to another) has made a comeback in the form of USB flash drives. Flash drives, which work with recent versions of all major operating systems, operate like removable disk drives but are about the size of your thumb (or smaller, especially if you have big thumbs) and have a shiny, rectangular plug at one end.

Some geeks carry the on lanyards around their necks, in their pocketknives, or on their keychains; they are available for under $15. To use one, just plug it into a USB port on your computer. After you copy whatever files you want, you need to tell your operating system that you’re done with the drive before you unplug it. Windows uses a tiny icon in the system tray for this task. On Macs, drag the Disk icon to the trash.

USB keys are surprisingly vulnerable to viruses. Don’t use one if you don’t know where it came from. Nerd gossip says that the Stuxnet virus was spread to Iranian centrifuge plants by having someone drop infected USB keys in the parking lot, trusting people to pick them up and plug them in, to try to see what was on them.

If your computer has a CD or DVD writer, you can also burn your files on a CD or DVD to give to your friend. It isn’t as cute and compact as a USB drive, but it’s more durable. Your camera’s memory card can also hold files.

I’m worried about ID theft

The U.S. Federal Trade Commission offers this advice to prevent identity theft: First, look out for phishing, or email that claims to come from a bank or another online account, such as eBay, and claims that your account has a problem that you can clean up by clicking a link in the message. These messages are never real, but they’re extremely dangerous. If your bank thinks that a security problem exists, it doesn’t tell you by email. If you aren’t sure, contact the company by phone or type its web address into your browser by hand and look for the customer service section.

The Internet isn’t the only source of information about you. Keep bills and other documents that bear your account and Social Security numbers in a safe place, and tear up or shred old bank statements and credit card bills. Get a shredder that cross-cuts the paper into short strips rather than the cheaper shredders that make strips the length of the page; patient thieves can paste them together. Those offers for preapproved credit cards are also dangerous if they fall into the wrong hands, not to mention dangerous to your financial health if you accept them. Shred them or stop them altogether by calling 1-888-5OPTOUT or visiting Optoutprescreen.com. If your driver’s license still has your Social Security number on it, apply for a new license.

Get in the habit of looking over your bank and credit card statements when they arrive (or even earlier, online). Don’t worry about the bank’s arithmetic, but look for charges that you don’t remember incurring. If you find any, contact your bank or credit card company immediately. After you verify any fraudulent charges, tell the bank that you want new accounts with new credit card numbers. You may also need to file a police report.

I can’t remember all my website passwords

The standard advice is to construct passwords from a mixture of letters, numbers, and special symbols; to have a different password for every account; to never write down passwords; and to change them every few months. Most Internet users who have dozens of accounts ignore this advice because only a truly unusual person can remember dozens of different random passwords and which account goes with each one.

Consider a compromise. Make up one good password to use on all your low-risk accounts ― accounts in which letting someone else gain access has little consequence, such as online newspaper subscriptions. Use different passwords for the accounts that truly matter, such as online banking. If you feel that it’s necessary, writing down these passwords and keeping them in a safe place like your wallet is better than picking a password that’s easy for someone to guess.

Don’t list your passwords in your desktop Rolodex or on a sticky note stuck to your computer’s monitor. Never, ever choose a password that is a regular English word (a word that appears in a dictionary) or a common name. Do add punctuation and numbers to your passwords.

Another option is to store your passwords in a password-protected file. The free, open source KeePass program enables you to create an entry for every website or other password you need to remember. You can enter a username, a password, a web address (a URL), and notes about the account, and you can organize accounts into categories (for example, Home Banking, Email and Chat, and Shopping). KeePass can also suggest extremely strong passwords for you (made of random strings of characters) and can copy a username and password into your computer’s Clipboard for pasting into your browser. Of course, you need to remember the password to your KeePass file ― don’t write it anywhere!

Some decent programs are available for safely storing passwords on smartphones and tablets. Be sure to pick an extremely strong master password and have a backup plan for when your phone falls into the bathtub and dies. (Waterproof ink on paper has stood the test of time.)

I’m worried that Facebook, Google Docs, and Google Calendar will lose my data

Okay, most people don’t keep anything all that earth-shattering on Facebook, but we keep our family calendar on Google Calendar, and many home and business users keep all kinds of important documents and spreadsheets on Google Docs.

There is one backup service that can back up these and other kinds of information. Backupify can back up Google Docs and calendars, the address book (contacts) in your Gmail account, your Twitter tweets, Facebook postings, Blogger blogs, and other information. Backing up a few accounts is free, and reasonably priced for more.

I get messages telling me that email I never sent is undeliverable

You can’t do much about this problem after it has happened. Most spammers use computers that have been taken over by worms or viruses to send spam, using faked return addresses taken from the list of spam addresses. Make sure that your computer isn’t the source of this type of unwanted message by keeping its operating system and antivirus software up-to-date, using a router as your firewall, and turning off the computer (or at least its connection to the Internet) when it isn’t in use.

People seem to know a lot about me

The rate at which everyone is losing privacy is scary. Here are a few tips.

Get rid of spyware that may be lurking on your machine

Spyware does just what it sounds like ― it spies on you and your activities. You think your Internet activities are private, but unless you keep your PC spyware free, they aren’t. Browse one mortgage lender site and you’ll hear from the universe of mortgage lenders. Buy from one pharmacy and you’ll receive solicitations from other companies for drugs you didn’t even know existed. Your inbox is full of names that closely resemble ― but aren’t quite ― people you actually know.

If all this sounds familiar, chances are good that software is recording your every keystroke. Get rid of it! (The software, not the keyboard.) Because it’s so widely used, Internet Explorer is targeted by hackers all over the world, which is why we use Firefox, Google Chrome, or Safari instead.

Don’t be dumb

Don’t put information on your web page that you don’t want everyone in the world to know. In particular, don’t include your home address and phone number unless you want calls and visits. Why would Internet users need this information, anyway? They can send you email!

Don’t order stuff while using a public PC

Normally, ordering products over the web or by email is safe ― at least as safe as handing your credit card to a server at a restaurant. However, some shopping sites store information about you (including a link to your mailing address and payment information) on your computer in a file known as a cookie. This system works perfectly when you’re ordering from your own computer ― you don’t have to retype all the info when you visit the site the next time you order.

But when you order stuff at the library or at a cybercafé, this personal information may be stored on that computer. The next person who uses the computer and goes to the site then has all your personal data available and may be able to use it to place an order. Better not chance it.

I can’t get my kids, spouse, or significant other off the computer

Games and instant messaging are highly addictive and seem to be becoming more so. Former Microsoft CEO Steve Ballmer brags about the addictive nature of the games his company sells and smiles as he says he wouldn’t let his kid play them. That ought to give you a hint.

Set clear limits on computer usage and stick to them. Have a talk with your spouse or significant other about which kinds of online chatting are okay and which aren’t. Also think about how much time you spend in front of a computer screen. Use some of your Internet time to make a list of outside activities you enjoy and stick it next to your computer screen.

On the other hand, if it’s your spouse, sometimes it makes more sense to squander $400 on a second computer or a tablet than to squander your marriage.

When I click a link, my browser says “404 Page Not Found”

Web pages move about or disappear on the Internet. If you type a URL from a printed source, make sure that you type the URL exactly as it was printed, including capitalization. If you read a URL that’s part of a sentence, watch out for the comma, period, or hyphen at the end. The comma, period, or hyphen may or may not be part of the URL ― or it may be punctuation for the sentence.

If you clicked a hypertext link or you’re sure that you typed the URL correctly and you still see this error message, the data on the site may have been reorganized. Try “walking up” the URL by deleting the portion back to the last slash character and trying again; and then delete the portion back to the next-to-last slash character; and so on.

If you see a File Not Found message when you try entering this line, for example:

epicurious.com/cooking/menus/cooknow/omelettes.html

try entering these lines, in order:

epicurious.com/cooking/menus/cooknow
epicurious.com/cooking/menus
epicurious.com/cooking

At one of these levels, you may find a hint about where the file you seek can be found. Alternatively, go to your favorite search engine and search for it.

A page long gone may still be found on the Wayback Machine, a free site that has attempted the daunting task of periodically saving snapshots of the whole World Wide Web.

I want to include my email address on my web page

Including your email address in a web page is a sure way to attract spam. Spammers have programs that crawl the web looking for email addresses to spam. You can thwart them by describing your email address rather than just typing it or use obscure HTML coding on the web page. At the least, you should set up a separate email address for your website at a free webmail site. If the flood of unwanted mail becomes too great, you can abandon that account and set up a new one.

One useful trick is to ask website visitors to include a special word in the subject line of their messages. For example, if your web page is about belt buckle collecting, you can ask correspondents to include buckles in the subject line. You can send the rest of the messages to the trash.