If you think running your favorite game is a good stress of your CPU, you're wrong. Games are only good for testing GPU. If you want to squeeze your CPU hard then use Prime95.
Prime95 (32bit) - 25.11 Download - EXTREME Overclocking
Prime95 (64bit) - 25.11 Download - EXTREME Overclocking
Download it, execute it and do some Stress Testing. Your system should be able to finish any of the tests without any errors or crashing. If something blue screens, you're likely to have a thermal, power or RAM issue with your box.
