Is your computer sitting on something unstable, like a cardboard box or something? A few years ago I set up a computer for my family, and since the tower was small, and sitting on the floor, they put an empty printer box under it to lift it up a bit. It went through 2 HDs in 3 months time, both quantum fireball's. When I replaced the drive the second time, I took it off the box and set it on the floor. The drive is working fine to this day. 🙂 I don't have any solid proof that it was the box, but my guess is the case vibrated more than it should, and possible was knocked by the user a little bit more, leading to the destruction of the drive. But this is all just speculation. 🙂
Side Note:
Is there something wrong with the HPT chipset? I bought a board with RAID support, and I'm using it just as extra IDE channels....