Vernon from TN writes:
Since hard drive failure is one of our greatest fears, does it make any sense to routinely replace a primary hard drive in an otherwise well functioning computer? If so, when and how?
Hard drive failure is a great fear, especially when you have thousands of photos, documents and songs that you can’t easily replace.
The first step to good hard drive maintenance is to use a S.M.A.R.T. (short for Self Monitoring Analysis and Reporting Technology) reading program, which can give you an indication if your hard drive is experiencing errors or being exposed to very high heat – which is known to shorten the lifespan of the hard drive. Active@ makes a great utility called Hard Disk Monitor which allows you to read the S.M.A.R.T. status (and it even tells you what the numbers mean, and which numbers you want high or low). This utility is available as a 14 day free trial at http://disk-monitor.com/ 
The second step is to try to fix anything that may be shortening your hard drive’s lifespan.The big enemies of a hard drive, outside of inherit mechanical failure, are heat and power loss. Heat can be a result of a case that’s filled with dust, animal hair and other things that have built up over the years.
The easiest way to clean your system out is to use compressed air and spray the fans, boards and components off. If you’re doing this, make sure not to spray any of the liquid compressed air, and take care to discharge any static on your body before touching computer components.
You can fix the power loss issue by owning a high quality battery backup power protector (available in most office superstores starting at $50), which will prevent a power loss from causing a read/writer operating to fail – or worse, a hard drive to not return its write head to the resting position. Most modern hard drives automatically return to rest when there is a power loss, but why tempt fate?
The third step is to replace your hard drive before it dies. This is easier than you might think, and you can use modern drive cloning programs (such as Laplink Diskimage  ) to make an exact copy of your hard drive. On a desktop computer, it is as easy as plugging in the second hard drive into your machine, making a copy, then removing the old hard drive. The process is much the same for a laptop, except that you would need an external USB adapter to load the second hard drive to make the copy.
Also, make sure you buy the right type of hard drive. To tell what type of hard drive you have (IDE or Sata) see the picture below.
Once the copy is done, you remove the old hard drive and connect only the new one and your computer should be none the wiser happy with a brand new hard drive in it.
Note: Upgrading your hard drive is a great time to consider faster/bigger hard drives. Many desktops come with 5400 RPM drives, and while being cheaper they do not offer the performance of 7200 RPM drives or 10,000 RPM drives.