sounds in everything like PSU not giving enough power, i had the same problem when i went from a 8800GTS 512MB to GTX 570, had to buy a new PSU (happens when the graphics card demand for power is not met, then it tries to divert power from other components like the CPU, the MoBo detects the power fluctuation as an instability and for protection shuts down the system); if you do that don't go cheap, you'll regret it. also, is the PC new, upgraded any parts recently?
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