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By Dan Gookin

You may occasionally try to open a file and find that it won’t open. If so, you probably see a dialog box instead. Before you go surfing around the dialog box, bear in mind a couple of things.

First thing to note: The reason the file doesn’t open is that your computer lacks the software to open it. That’s a fact. If someone emailed you the file, email them back and explain that you cannot open the file. Your situation isn’t your own fault; the other person needs to send the file in the proper format.

Second thing to note: Some files aren’t worth opening. Don’t even try. The file may just be binary code that a human wouldn’t understand or appreciate anyway.

When the mood hits you, however, you do have a choice: In Windows XP, you see a dialog box with an Open With button. Click the button. It opens the same type of dialog box displayed immediately by Windows 7 and Windows Vista.


In the dialog box, you can choose the option Use the Web Service to Find the Correct Program, but the odds are good that the search turns up empty. Instead, choose the second option, Select a Program from a List of Installed Programs. When you do, you see the Open With dialog box.


The Open With dialog box is used to open a file with a specific program.

The first thing to do is remove the check mark by the option Always Use the Selected Program to Open This Kind of File. When you fail to do so, you perform the process of file association, which probably isn’t wise to do at this point.

One program listed in the window might open the file in a readable state. My suggestion is to try Notepad first. Notepad can easily view text files, and many mystery files are text files.

When Notepad doesn’t work, you can try Internet Explorer, which recognizes a wide swath of different programs.

Some people have a temptation to peek around in a computer. It is a wonderful trait to be curious. But there’s also a danger. The danger is that it’s a bad thing to delete or change any file you didn’t create yourself. Just because you don’t understand a file, or can delete the file and not see any immediate change, doesn’t mean that the computer is okay.

  • Don’t delete any file you didn’t yourself create.

  • Likewise, don’t rename, move, or modify any file you didn’t create.