I have an ASUS computer with two hard drives: first drive has Vista, which is working fine, and second drive has 7 with win explorer constantly restarting. I have gone through the process of trying to repair and also go back to a restore point; I have also tried disconnecting everything extraneous. It seems the OS is corrupted, but I have lost the discs that I used to install it, so can't use them to repair. I bought a repair USB thumb drive, but don't have the option of booting from USB on the boot menu, only "boot from removable device" which doesn't seem to work. I think that if I can get to the activation key information that's stored on the E drive through the C drive, I can download a repair. Any suggestions?