|My memory I am assuming you mead a hard disk. Memory is RAM, a different thing altogether.|
As it is an old computer I am assuming that the hard disks are P-ATA. If so are these two drives on the same cable? Are the jumpers properly configured for slave and master. If it is on the same cable as the CD/DVD drive one still needs to be configured for slave and master.
If they are SATA drives then its a different ball game altogether.