Western Digital, Maxtor, Quantum, Seagate, IBM and Fujitsu all make good hard drives.
Personally I favour IBM, but all of those are good drives.
ATA100 makes no difference, and 7200rpm is the way to go.
<< IBM 40GB GV, 5400rpm, ATA/100, 512K buffer VS. Maxtor 40GB, 7200rpm, ATA/66? >>
Option 2. The 40GV is IBM's value line, the 75GXP would be more comparable to the Diamond Max + 40gig.