Ok every time I go to play diablo 2 after round about 10mins to 2hrs or so my comp crashes and won't turn on for at least 10 mins or so even then it take 5 atempts to get it running.

Anyone have a clue to whats happening at all?

keyboard issue i think

yeah normally helps if I type something

This only happen to you since the LAN at all?
IF so, reseat your mobo board or check that something isn't causing a short

Take the entire system apart and clean it. Take all the cards out and the ram. You can leave in the CPU.
Use a paintbrush to get all the dust off and some PCB cleaning spray to really clean it properly. Make sure you clean it properly. Put it back together and see if it works properly now.

Sounds like either your PSU has problems or youv got a power problem on your mainboard. Grab someones spare PSU and try it out, if that fails, I daresay your bored is shagged.

and if it's an old board look for leaking capacitors specially if it's Soltek or equivalent s***.