Compaq deskpro 2000 prob.

[imparanoid]

i have an old compaq deskpro 2000 im trying to sell but i cant get my harddrive to work ( and my keyboared input went out so im getting a usb card and a usb 2 ps/2 plug) i have an newer comp that had an old 4 giger inside so i decided to get a 40 gig and give the old comp the 4 giger but the prob of not being able to get into the bios to tell me comp to boot frm the floppy i had to do it on my other comp well i install win 98 and put it in the old comp but all it says is 'non system disk remove disk and replace with sys. disk' so i tryed its old hd and the 4 giger together ... it work so i deleted the old hd and tryed them both the oldclean and the new with win 98 but i stoped working an suggestions?