Well, it's fixed. seems like some BIOS setting was fucking up teh bootup, and not the drive, who is working like a charm! I love WD :P
I booted with a diskette and saw all the contents of teh drive were there, so I thought WTF!
Fiddled around with the BIOS and now boots again, and as master (with a ZIP as secondary)
It's hooked with the 80 cable ribbon, to primary IDE0. I dont know how to activate UDMA but the drive's manual doesnt say a thing about it being UDMA compliant! It's a WD Caviar 38400.
Anyway, thanks for your help! Much apreciated!