Windows 7: Computer wont stay running overnight

i left my computer running last night downloading 2 games though Steam, when i got up it was off, unexpected shutdown. This has been happening a lot and Ive been trying to fix it but not sure what causing it. i deleted all the logs before i walked away from computer before bed, no mini dump was created or in the LiveKernelReports\WATCHDOG folder. I'm lost on the cause and I'm not sure what i need to do.

is it overheating?
you might try watching the temps could be thermal shutdown which isnt good
u might try useinghwmonitor to keep an eye on your temps

no i dont think its overheating, i got 2 120mm front fans for intake, a side 240mm for intake, and 2 120mm top for exhaust and its a huge full tower case

hers the data from HWMoniter though

max temp is from play Crysis for an hour on Very High settings

im still get alot of unexpected shutdowns, and there isnt any logs being saved. No minidmp file, folder is empty. i posting an XML file of the event veiwer, there is alot of errors and critical events over the last few days. i really need some help with this, i cant figure out whats going on. i can play games all day with no shut downs, but i leave it at idle for a little bit and it does an unexpected shutdown