Windows Vista How do I get rid of it???

This has turned into a nightmare. My son paid for and downloaded Windows Vista and now all his stuff went off into left field and it won’t recognize his CD/DVD player. I’d like to just format the drive and reload WINXPHOME or FDISK to delete the partition and reload from there. It over wrote the CD/DVD driver so it won’t even boot from the CD, evven after changing the boot sequence from BIOS. I wish he’d have asked me first and I’d have told him NO WAY.