Red line lock up
 

I've never come across this problem before, can anyone help?
A neighbour has just installed a new version of Office. Since then, every now and again the PC locks up and a red line appears across the screen. The 3 finger salute won't restart and neither will the reset button. The machine has to be powered off. My immediate reaction is to reinstall office but has anyone come across this before?

It is possible it was overheating as the bearing of the fan on the CPU heatsink was getting increasingly noisy. I have replaced it tonight with a more powerful fan. However even when overclocking my own PC's I have never seen a red line across the screen.

Might be a vidcard issue? If cpu fan was knackered maybe the gfx card (if it has one) is to, and its overheating.

Graphics card is so slow it only has a passive heatsink.
The computer is an 1800 Athlon running XP.
Thanks for the reply.