Uninstall everything you can normally, then use the Add/Remove feature from your control panel. Scan your drive's whole registry, and delete everything that you FIRMLY believe belongs to the game. If this step makes uncomfortable, download this
and run it once. It should clear things up. You may also want to run Check disk, delete some unnecessary files, and defragment your drive(all from control panel).
Check your CD or damage or dirt, shut off all security, and try to reinstall.