Thanks for the replies
I don't think the problem is the CD-ROM because I have used the same one in another system to boot and install.
Though now, I've managed to get this install to work, but I'm using floppies to do the initial boot, and then "redirect" the boot to the Cd-ROM. Which is currently working. It's formatting the C: drive at the moment, but when the install is finished, I'll put in a better CD-ROM to test eveyone's theory.
If anyone is curious, or if this maybe helps, it is a Compaq DeskPro EN
(This is what it says on the top panel cover)