Yea, could you please post a COMPLETE list of your PC specs? If it is a power supply shortage then you will need to get a replacement part.. If you computer stays on for long enough run the Prime95 like I previously suggested. I will post a link for the 32 and 64 bit version. You will PROBABLY need to run the 64bit unless your PC is specified to be 32 bit. Check it by going to start, right click on computer, and then go to properties.
32 bit: http://files.extremeoverclocking.com/file.php?f=103
64 bit: http://files.extremeoverclocking.com/file.php?f=205
Any questions on Prime95 just go to YouTube. There are some pretty good guide videos which will be more helpful then me typing out all the necessary steps to test your system.