Well confirm any specific events in Event Viewer (as stated by CCT)
You are able to get to Event Viewer by clicking on Start->Run-> eventvwr.msc
Have a look for and Minidumps created and then attach them
http://www.techspot.com/vb/images/editor/attach.gif here in a new reply
You are able to get to the Minidump folder by clicking on Start->Run-> %windir%\Minidump
Many seemingly hardware related issues can be caused by faulty drivers
Go to your Computer's or Motherboard's support page, and confirm all drivers are up to date
Many seemingly hardware related issues can be caused by software (such as Norton)
Try uninstalling any highly intensive software packages or virtual softwares
This can be a fault with your Ram (faulty ram can cause many varied issues)
Please run Memtest (
http://www.techspot.com/vb/post653029-21.html)on your Ram
Otherwise this can be a faulty connection, or even just one hardware component
Have a look at Benchtesting (http://www.techsupportforum.com/1010960-post1.html)your motherboard
By the way, even though your Power Supply may work it could still be faulty (due to incorrect voltages)
You could test with a known working PowerSupply.
There you go, that will do for a start