I tried a few times but no joy :( So I left it alone for a half hour or so then tried again, This time it did start so I booted into safe mode and copied all of the "My Documents" folder to a removable drive.
It has started OK today, but I'm expecting problems. I wonder if it's getting too hot? Ah well, I'll get off now and get something to eat. I'll be on-line again later, so maybe catch later.