i've been having problems with pc for the last few days. it's keeps crashing when i'm playing games.

i've tried doing disk cleanup, installed new drivers for graphics card & even turned off anti virus & firewall. nothing seems to work. after a few mins of play on the last 3 games i've tried, the pc just resets. it loads as normal back to desktop with no error message or anything.

in my efforts to try and fix this, i went into bios & tried changing a few thing around to see if that did anything. but my last attempt seems to have killed my pc. i changed the setting in bios to "safe" (i think thats what it was called, the option next to optimal settings), and now my pc won't even boot. all thats on screen is the bios version at the top, then the processor (which shows around 1000mhz instead of 3000+) and it does memory test, but then it freezes. i can't even access bios to change the setting back.

have i totally messed it up, or is there a way to sort it out?

please help.