Upgrade Your MacBook's Internal Hard Drive
Besides adding a hard drive, you can upgrade your internal drive, which can be a hassle. As does a memory upgrade, adding or swapping an internal drive involves opening your MacBook’s case. In fact, it’s a somewhat more complex procedure than adding memory.
Add a second drive rather than swap out an existing drive. You’ll avoid the hassle of backing up and restoring your system on a new drive or (even worse) reinstalling Mac OS X and then reinstalling all the applications that you use. (Swapping a hard drive should be the definition of the word hassle.)
Instead, add a second drive and leave your current hard drive as is (or if you’re already using an external drive as a Time Machine backup, add a second external drive).
However, here are a number of very important reasons why many MacBook owners choose updating internal drives, even with the hassle of swapping:
They’re cheaper. You’ll spend significantly less on an internal drive because it doesn’t need the case and additional electronics required by an external drive.
They’re faster. A typical USB 2.0 drive isn’t as fast as an internal drive.
They take up less space in your work area. An internal drive eliminates the space taken by an external drive, which can range anywhere from the size of a paperback to the size of a hardback book.
After you establish that you are in fact ready for more space — and you’ve decided whether you want to add an external drive, or (if you enjoy punishment) upgrade your existing internal drive — you’re ready to consider how big of a drive you need.