Thanks, guys.
I used to think I was Geek level 3, but now languish below zero with BOAC!
After the spontaneous reboots, which were random and sudden I was given the window telling me that the computer was recovering froma serious error. Filing the error report automatically started up a microsoft help site, which wasn't much help.
I don't recall ever downloading anything called Jingle.zip, but may have done some time ago. A long time ago.
By co-incidence, I was recommended to download a security software called 'Rapport' by HSBC online banking last week, which I did. It has caused such a slow down of my computer, that yesterday, I uninstalled it. Voila! the reboots have stopped, so there is suspect number one. I also did a disc cleanup and general go through of stuff I have which isn't used.
It might mean this old boiler (XP SP3) Some pedestrian Athlon chip, can't remember what speed, can soldier on a bit longer.
Thanks again