I don't know this machine, but when I see that it's a P100, I am reasonably certain it does not support big hard drives. WD has a DOS program that comes with the drive software called EZ BIOS which is supposed to make old machines support big drives. If you have the manual that came with the drive, read the section on EZ BIOS. PCBUILD Digest - 19 Jun 2001 to 20 Jun 2001 (#2001-172)I'm working with a Compaq 5100 (P100) machine and trying to install an additional hard drive. I tried to install a Western Digital 20 gig drive, but "setup" misreported the size, and it wouldn't fdisk. Anyone know if there's any bios limitations (I believe the machine's been updated with the latest setup files...) on hard disk size for this series of Compaq? My emails to Compaq support have gone unanswered.....Please Help!! Thanks!!! Do you want to signoff PCBUILD or just change to Digest mode - visit our web site: http://freepctech.com/pcbuild.shtml