Hard Disk Stress Test: Needed? Best Testers?

So let's say you're hearing terrible sounds from your hard disk, but your drive appears to performing properly, even passing bad sector tests.

Would it make sense to stress the hard disk to test its reliability? If so, what are good tools out there?

I doubt many HDD tests can detect the kinds of problems that make "terrible sounds". They may be able to detect frequent read errors causing frequent head seek operations; I'd bet the manufacturer's free test suite will do that test. But if you have a failing bearing on a drive spindle my guess is they don't build in vibration analysis systems. "Stress Testing", on the other hand, sounds like working it hard until it fails. Then what? Once it's failed it can be hard to recover.

Try to create Backup of the "noisy" hdd onto a separate hdd more often, You can try using the free version of HD Tune available at http://www.hdtune.com/ to stress test the "suspect" hdd

Try SeaTools (works just fine with non-Seagate drives). Run the short and long generic tests, and the short and long self tests. If it passes all of those, it should be good to go.