Is tha old hard drive you added listed accurately in the BIOS?
I have this old hard drive that was working earlier. I connected it the other day and it wouldn't show in my computer. I checked for it in disk management but it wasn't even there as unallocated. Any help would be greatly appreciated. The Hard drive is an Western Digital 16gb. It is not new.
Processor-2.2ghz AMD Athlon 64 X2 4200+
Boot Drive-300gb Seagate (Not the problem drive)
OS-Windows XP Pro SP2
P.S. Has anybody heard of having a slave drive that would stop your computer from booting?