Restarting computer alert!!!!!

My computer has frequently started to restart mostly during high spec gaming (counter-strike:source). I think it is because my cpu is heating up too much. What program would you recommend using to cool it down. I am not using over clocking and i hav reset bios to default.

 

softswares can not help you so much. put more back case fan, clean CPU heatsink
if you are looking for softs :
http://www.majorgeeks.com/downloads14.html

 

If it has just started happening as summer aproached could be heat,try running a benchamark 3dmark 2003 and have sandra or speed fan running in the background,they both can make graphs and give you an idea of how hot everything is getting