Its the Promise Ultra ATA/133 Controller. I just bought it today, along with a 80gb/Ata133 Maxtor Drive. I tried installing XP, it works the first time it boots up, then when i restart XP it hangs at the boot screen, and the blue line just keep moving, as if XP is doing something, but it never finish's booting. This is really starting to piss me off... any help would be appreciated... thx in advance.