I found a computer someone had thrown out and upon finding the video card bad, replaced it and it booted right up. The issue is that someone has an XP OS on there and I can't get past it so I was going to install another OS. I changed the boot order to boot from the CD first, but although the drive is powering on and accepting the CD/DVD, its not booting from the disk. I've tried 3 different drives, 3 different OS CDs/DVDs, and when I switch the Hard disk ribbon with the CD/DVD ribbon, the hard drive works on both ports, so I'm assuming its not a problem at the port. The computer is reading the DVD/CD drives and displaying them in the BIOS with their names, but it just won't boot. Any suggestions?
I thought I'd add that it isn't reading the disc at all. It's as if no disc is in the drive.

Sorry, another edit, I tried switching out the ribbons too, and that's not the issue either.