Drive Health is a Windows program that helps you to estimate your hard disks Life Resource. This tool allows you to predict possible HDD failure and prevent losing the critical data. To estimate hard disk life our program uses special S.M.A.R.T. technology that is supported by the most of hard disk manufacturers. By implementing this technology the Drive Health provides access to the hard disk drives reliability monitoring, and keeps you informed about any potentially dangerous degradations of performance or reliability of your HDDs. The monitoring program eats minimum CPU and memory resources and can be run as a NT service.
http://www.drivehealth.com
Its good for predicting hard drive failures, only takes up 150kb of RAM, and runs in the background as a service with no taskbar or system tray icon. I recommend this tool to everyone
You might find that it predicts a hard drive failure after a couple of hours monitoring (on my mates's PC that happened), its probably normal since it needs at least 2 weeks to learn how your hard drive works.