Seems I was a bit premature.
It will crash in safe mode (BSOD) when asked to do anything too tasking.
EG backing up files to an external hard drive. After about a minute of backing up it crashes. Attempting to use system restore causes it to crash also.
I have the codes from the BSOD screen though, but don't know how to interpret them. Searched MS website etc but it's not finding my specific problem. Where do I find this debugger? Is it a generic program or is it part of the windows suite?
"Reinstall repair" looks favourite.
Thanks again for your continued advice.