So, I'm borrowing a computer for school. I don't know what happens to the computers once they've been returned, but I don't trust that they'll erase the hard drive before giving it away again. Anyway, I've had to restore my computer with system repair/re-imaging discs (so the system was reverted back to the way it was when I first got it) more than once before, and I'm fairly sure those discs don't erase everything on the hard drive (I could be wrong though). I recently erased the unused disk space on C:\, can I rest assured the data and files that were on the computer before I recovered the system are most likely gone for good? This is pretty important because I don't want there to be any potentially recoverable sensitive data on this hard drive, including data from before the system recovery.