Try put in a bootable CD (e.g., Windows install CD or GNU/Linux distribution CD) into this drive and see if it's booting. If it works, then it's a software problem. Try reinstalling the OS. If not, then I'm afraid that it's a hardware problem.
You try another cd? If it was working fine and you put in another (blank cd?)and it stopped it sounds like something is wrong with the media. Try some other discs, then reinstall the burner software before you reinstall the OS. It does look like a software issue.