download and run this ... it has a "torture test" let it run overnight
its a well known pc testing tool
http://www.mersenne.org/freesoft/if it has any problems then either your ram, cpu , mb etc are bad or overheating....
if it runs fine then you know it's a graphics card problem....
either way my bet is hardware issue, computer should never reboot like that ever.
Tips if this helps you any
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