mmm - hard to say what is causing the reboot - could be a very corrupt sector on the drive that is causing Windows to bomb out (data recovery tools scan all sectors).
Try following these instructions, but STOP the search before you get to the problem part, and note down where the search is up to in the progress window:
http://forums.getdata.com/computer-d...ard-drive.html
Then run the search again, but this time, first go to OPTIONS > ADVANCED > and put a tick in "prompt for start cluster".
When you run the search on the physical drive again, you will be prompted for a starting location. The idea is to enter a starting point just past the bad sector so you can continue to scan the rest of the drive.
Good luck.