Reboot mystery

I have 2 rigs with Identical motherboards. My main one had a very bad power surge problem and created all sorts of mayhem to numerous to mention but here is the rub. The mobo that was in situe when the burn out occured I put in my secondary computer which of course have totally different hard drives etc. one with an OS which boots fine and runs OK, BUT, every 2 hours to the minute the rig reboots, No warning just does a custom reboot closing progs as it normally does. Obviously it is not the OS as I said previously its a different HD and OS. So the only conclusion I can come to is that some mal function on the mobo is causing this. Have of corse reset the CMOS and went as far as leaving the battery out for 24 hrs. Any ideas fellow Geeks. ??

 

Does it shut down after two hours using two different HDs/Os(s)?

A quick search turns up that Win7 Release Candidate OS is programmed to turn off every two hours after expiration. Could you be using that?

 

Thats exactly what it is sach2 ... as I said its a secondary computer and rarely gets used so I must have loaded that version a while ago. Strange how it has suddenly decided to work though (the timer) perhaps I have never ran it for 2 hours before. Thanks once again