Raid-1 trashing drive 1

Having a tough time figuring out why one of my clients server keeps crashing hard drives. The server has a Seagate IDE primary hard drive with nothing but Win2000 installed on it and 2 Seagate Cheetah 20 GB hard drives set up as Raid-1, mirrored. The two drives are in hot swappable cages. The raid controller card is an Adaptec(not sure the model #) that we have replaced twice under warranty. The problem is drive 1 of the raid array has crashed 4 times each time having to be replaced also under warranty. Everything works perfectly for a month or two, then raid has to be rebuilt and works for a while then after one or two rebuilds the raid bios says the drive is damaged. This problem has never affected drive two. I have taken the crashed drives back to my shop and sure enough they are dead. I have checked the power supply and it appears to be running at acceptable levels. The server is attached to an APS 1000 ups, so I know it's not getting hit with voltage surges or dropouts and it does not have a modem installed, so the phone lines don't come into play. It's got me stumped, does anyone have ANY ideas? :confused: :eek: :confused: :(