If, however, you want a hard drive to store pictures, movies, or music on, you might want to buy based on size. 100 gigabytes will cover most home user needs, but if you’re storing video, go for something bigger. 200 or 300 gigabytes is the recommended hard drive size for storing uncompressed video; music and picture files are much smaller.
If you buy an internal drive, it will likely cost a lot less than an external drive; remember to make the same basic considerations. With an internal drive, 100 gigabytes will more than last most home users; if you’re using your computer for email, internet, a few games, and some mp3s, 100 gigabytes is more than enough. You might want to consider buying an even smaller drive; no use buying what you don’t need. 40 gigabytes will be fine if you want a computer for basic home use. Business hard drives usually don’t need to be any larger than this, either.
Laptop hard drives can also be generally kept small; 20 gigabytes is standard, 40 gigabytes is usually more than enough. If you need more for movies or music, an upgrade to 60 or 80 gigabytes shouldn’t be too much more expensive.
Speed
For home and business PCs, the speed of a drive won’t be incredibly important. 7200 RPM (Rotations Per Minute) is recommended; if the RPM’s far slower than that, your drive might not keep up with you.
While there is nothing wrong with a faster drive, it’s possible that faster speeds increase the chance of drive failure. Unless you have a specific reason to buy a lightning fast drive, don’t buy based on a drive’s RPM.