Firstly check your temperatures on HWMonitor... If you don't have that download it from here :
http://www.cpuid.com/downloads/hwmonitor/1.24-setup.exe
Then check your stability, for that download Prime95 from here : http://www.mersenne.org/freesoft/
Do a stress test and see if you get any error or not... Generally you may get BSOD...
If the temperatures are higher than 75°C then you should try to change the thermal paste applied... and then check the temperatures... If still you are getting high temperatures then change your CPU cooler....
And stop all the processes when using Prime95... First open HWMonitor and then put it in side so that you can see it and put Prime95 on other side and start the stress test and see the maximum temperature of your processor....