I feel your pain. I had the blue screen of death during install - four times (32 bit twice, 64 bit twice); the last install was 64 bit and then for the fun of it, I tried booting - which succeeded. So my Windows 7 is in an undefined state. There is a recovery tool - maybe that can go through all files and replace anyone with a mismatched hash. Pure dumb luck has it that the system does appear as good as fully functional.