Random restarts, BSOD, and OC failures

So about 2 weeks ago i decided to reformat and was going to use my vista CD but decided to go for windows 7. It worked fine for a bit but then every few days id get a random crash, or BSOD, and after restarting would get a "windows has recovered from an error...etc" and sometimes a scandisk check before bootup.

The monitor would suddenly shut off and the light on the bottom which is usually blue became orange. I restarted several times and disabled overclock but my comp wouldnt start up again so i removed the radeon 4870 i had hooked up to my monitor, moved the other 4870 (i have crossfire) into the slot the first one was in and hooked up my monitor to it and it worked fine then. Then just today only 2 days later i was in the bathroom for about 30min, i come back, and the screen randomly turned off. I restarted, i got a "failed to overclock" error so i disabled overclock then i restarted again and it did a check disk again. I read somewhere it might be my sleep settings messing stuff up cus my drivers are bad but i did fresh flash of the latest 0902 asus drivers for my mobo twice. Is it really the sleep settings, are my bios drivers bugged, my video cards bugged, or is windows 7 the problem? I switched to 7 cus i heard it was faster even tho for almost 2 years of using vista i never had a single problem with it ever.

my comp specs are in my profile i have a custom built PC i put together in mid 2008.