<< depending on the height your dell can take. the ibm travelstar 60gh is one of the best. or the toshiba mk4018gax.
both of those are 20 gig platters and 5400rpm. the toshiba i cant find at any store, but its 9.5mm 40 gig and 8mb cache. the ibm is 12.5mm 60 gigs and 2mb cache. >>
Correct me if I'm wrong, but isn't the Toshiba a 16mb buffer drive?
BTW, the upcoming IBM 40GNX will also be 5400rpm, 40gb, and 9.5mm thick.