Windows 2000 Server

HI,
I’m installing the os (windows 2000 server) on a pent II 266 mhz computer w/256 mg memory. When ever I install any service pak and restart the computer I get the following message on the blue screen — inaccessible_boot_device. I tried service pak 2,3
with the same results. I’ve tried repairing the windows installation w/the same results…The hard drive has no problems.. The computer runs fine until I install a service pak. Any help would be appreciated.