I was saving a project in an application(Cubase SX) when I got the Blue Screen with a 'Hard Error' message. The machine rebooted, scanned D: drive, found loads of bad folders - folders that never existed before - then went back to the Hard Error. Tried rebooting, same thing. Is my disk hosed? What can I do to recover? Thank you.

Not all programmers are created equal. Some programs are not capable to deal with every computer configuration. If this is the only program that causes this to happen then just don't use it. Or use it when nothing else is running. You could turn off the reboot option, in the "startup and recovery" window, and see exactly why it's crashing.

The maching won't boot at all now. Not in safe mode or any other mode. No error, just hangs on a black screen.