Rebooting

Hi I have an XPS710 H2C with a factory overclocked x6800 that will not run overclocked, it has not since day 1. Once in a while I will try to overclock it (through the BIOS) but it is always a no go. Now I am having another issue with it, when I run a game it randomly reboots. It is not patterned ie: every 10 minutes but randomly 10 min the first time 35 minutes the next 5 min the one after that. I have an issue with not being able to run my PC overclocked as that is the very reason I bought it (I am talking to support often about this but so far it's the runaround). Do you think my processor could be faulty or not cooled properly. Any other thoughts would be welcomed





XPS710 H2C
x6800@2.93
4g ddr2 6400@800mhz
8800gtx