There are a lot of reasons you might want to test your hard drive for problems. One of the major reasons to perform a test would be if your hard drive is making strange noises. This can often be a sign of a failing drive, something a test can point out.
Some other reasons to test your hard drive would be if a defragmentation program directed you to do so or if normal troubleshooting steps for certain problems (like error messages in Windows) are of no help. Often times the last step is to diagnose a possible hard drive issue.
So what kinds of tests do you run? How do you do that?
Some of the best hard drive testing software programs are free! See my List of the Best Free Hard Drive Testing Tools for several that I recommend.
If you're a user of Windows XP or Windows Vista, Microsoft includes a program called Error Checking which can perform some very basic tests and can even attempt to correct errors as it finds them. Most other free hard drive testing programs are supported by the hard drive manufacturers themselves and are much more powerful. Seagate, Hitachi, and Western Digital all make very popular testing programs.
If the free programs aren't feature rich enough for you, there are a number of companies that create even more powerful testing and correcting tools. Here are a few of my favorite third party hard drive tools. They might seem a little pricey but depending on the value of the data on your dead or dying hard drive, it may be worth it to take a shot.