Thanks for the advice Duncan, Barry,
Dunc: an upgrade just isn't necessary.
We'll run this into the ground and if it falls
over there are a few similar spec PCs in the
house as a backup.
FWIW, I think I might have found the culprit though.
I removed this green adaptor from the PS2 port
and the Logitech Laser mouse.
USB mouse direct to a spare USB port.
No problems for 2 days now.....
Intermittent probs...dontcha hate em
Steve