PC Stats posted a beginner guide about diagnosing bad hard drives

The hard drive is the single most important device behind the mass acceptance of personal computers in the home and workplace. The ability to save significant amounts of data within a computer itself, rather than being forced to place it on external media finally fulfilled the potential that the PC had never quite lived up to, at least as a business tool. Hard disk storage ability has increased massively since the early days of the technology, and will likely continue to increase in the future as drive's cost per megabyte of storage drops equally fast.

Beginners Guides: Diagnosing Bad Hard Drives