The bad news - PC often fails even in Safe Mode.
Ian, I keep Startup to the absolute minimum. Basically jusy Kaspersky and BOINC which both run all the time.
I put in the original Windows CD looking for a Repair section but could only find a Complete Reinstall so I did that anyway. For a few minutes it seemed to be OK but then it froze up again.
At one point, whilst fiddling I got a message stating "Irreparable Hard Disk Problem" so I fear the worst.
Blasted thing is only four years old and this is the second hard drive, the first one having failed after 13 months.