Just to be clear. You installed all of the COD disks to your HDD ( you must had a big HDD) with a clean disk, meaning a disk with no scratches or laser burns. I am assuming the current disks you have now are all scratched? that's why you cant play them. I would recommend if you haven't done so, get a clean mw2 or any other COD disk from a friend or rental place. Re-install it to the HDD then put in your "scratched" disk and see if it works. It should. But you may have a dead laser. If so just take it to your local repair shop and have them replace the drive if you don't want to yourself. Hope this helped!