inaccessable_boot_device

I put 20 gig hard drive currently configured with Windows 2000 professional with valuable source code on it in to a new computer with a 900mghtz processor. When the computer boots it runs chkdsk and then tries to startup, when starting up it comes up with an error message “inaccessable_boot_device” The hard drive was to my knowlege working fine in the old computer. What could be the problem??