On at least two occasions I have heard a sort of clicking noise (one or two at the most) coming from my pc. I have a 40 GB hd primary and a 160GB ide hd slave. I'm not sure if this is my hard drive failing. I have listened to the "failing hard drive" samples on I think maxtor or sony's site and the first sample sounded similar to the noise I heard, only the noise didn't repeat over and over, it just sounded once or twice really quickly.
Also, my system has been crashing and I don't know if this is because of a program I installed or if it is my hard drive actually starting to fail. Is there a way to check what is causing it to crash? If I post the error report the next time it crashes, would someone be able to decipher what the cause is?

Occasional clicking is probably not anything to worry about.
Do standard maintenance; disk cleanup, error checking, defragmenter.
It could just be the click as the read head swings from one extreme to another because your drive needs to be optimized in that manner.

To see if the drive has problems; you should first make sure that if your BIOS support it that SMART is enabled for those drives. SMART will warn you if the drive is experiencing problems, which could lead to failure.

The other thing to do is to go to the drives manufacturer and download their diagnostic tool and run it. It will let you know if the drive has any problems and if you need to be prepared to replace it. If so it will produce a report to submit for warranty replacement if the drive is covered. In case you loose data for HDD failure, you may contact any reliable hard drive recovery lab. My friend told me about Salvage Data Recovery Lab at 76 Progress Drive Corporate Park; Stamford, CT 06902. I used their services couple of times for my office computers. Reliable and well experienced guys.