Raid5 array failing left and right. Help!

I have been having the issue for the past month with this same tower, while running in a raid5 array, every once in a while a drive will fail. I could see this being very easily solvable if only one drive failed, I could just replace it then. The problem however is that I've replaced two of the drives already, and I'm begining to think that the drives themselves arent what is failing.

Right now my current setup is a 64 bit edition of vista home premium, Ive got 2 gigs of ddr2 800 ram, 4 western digital caviar 160 gig drives, and a 2.4 GHz Intel Q6600. Video card is an 8600 GT, and I am running this all on a P35-DS3R.

The big issue that I have had with this is the fact that this issue is reoccuring all the time, on different drives. So far I've had every single one of my drives label itself as 'failed' at least once. This has even followed me through 3 different full wipes/reinstalls of the operating system. The drive gets labeled as failed on the bios as well. Something that had just recently struck my attention was the fact that I can now get the issue to occur in a repeatable fashion. Seems that whenever I try to install the newest updates MS has out and restart, a drive fails.

To be honest, I would be surprised if this was the OS's fault. I have yet to have any issues with this machine save the raid array issues. If someone could at least point me at what I might be doing wrong, I would be much obliged. Until then, I get to let my computer sit and rebuild parity for another 10 hours.