most of the oems I have seen have the cdrom if no dvd drive as master on the 2nd ide port
if you have 2 cdrom drives now you must check to see if the jumper on the back of first one is to set master not CS(cable select),use the plug farthest from motherboard.
the 2nd one set jumper to slave ,
if that does not work and you can use the 1st ide port
put the 2nd one on the plug left on cable leave it set to slave
only if hard drive is set to master if hard drive set to CS set also to cs.sometimes ya gotta play with config
watch you cables some machines use 2 diff cables to save on money hard drive is 80 wire 40 pin if ide ata
cdrom cable (OEM)can be 40 wire 40 pin
good Luck