Jan
I have ran into this many times.  It is usually a voltage drop on the
circuit that the computer is plugged into.  Plug it into a dedicated circuit
if you can.  Check for a laser printer on the same circuit and move it.
Once I had a computer that only failed in the morning right after the shop
opened.  The reason was the electric cofee pot on the same circuit.
Ron Taylor

>Periodically my computer shuts off & reboots.  The only time it does it is
>Jan