A while back I had an issue whereby I had a bad driver causing a BSOD at startup and I could not even get into safe mode. From googling around I found a way to reset the system registry so that it would boot up as if it was a fresh install but retained all the user settings. This involved renaming some file(s) and copying the original file(s) from another backup location at a command prompt (HIV's?). Well I have hit this issue again with a different PC and for the life of me I cannot find the guide. It's not simply a case of renaming the offending device driver file either as the BSOD does not give a name for any file. It's being caused by what I believe is the AHCI mode. Basically my brothers old motherboard died and he tried to move the hard disk to another PC. But I think when I installed Win7 for him on the motherboard that is now dead I set it to AHCI mode. But the motherboard he switched it to does not support AHCI mode. I know this because I have another brother who had to have his motherboard replaced (Sandybridge SATA issue) and I installed his the very same day (ironic) and we put his old drive back in and it had near enough the exact same issue. After some head scratching I switched the BIOS to AHCI mode and it booted no problem. So if anyone knows the trick of renaming and copying the first time bootup devices/registry/HIV wotnot then can you please let me know as I want to try this whenever I come across this type of issue again as it's not always possible to set the BIOS to ACHI mode and it's painful to have to reinstall Win7 from scratch.