Yes, that cured it. All that trouble caused by a blocked fan.
I downloaded CPUID to that machine and the CPU runs at around 30C.
So, XP re installed. I've lost my other applications that were on the Hard Drive, but I can get them back. Most of the data files were backed up.
Oh the joy of modern technology.
Thanks for the help.
Oh yes, Nearly forgot.
Tomorrow (Friday) I retire for the fifth and, hopefully final, time.