Screen Goes black but computer still responsive.

So basically my problem likes to show up only when it wants to. I have gone months to even a few days before it arises. Basically when i am playing a game i will get program is not responding then my computer screen will go black but the tower and everything is still running i can still hear everything and i can still play the game i just can see anything. First i thought maybe the monitor i tested 4 different monitors and the problem still persists. Then i thought Video card checked the drivers made sure everything up to date problem happens again. So then i buy a new video card dont see problem for several months then randomly happens so i checked the driver happens again so i buy a new video basically i tested 3 video and still have the issue so i don't think its my video cards. Now whats weird from time to time when it happens like i said its random it wont happen for months or it will do it for a few days straight. When the screen goes black i have to turn off the computer by holding the power button and it wont turn back on the tower starts i can hear all fans starting up but nothing on screen. If i unplug the power cord for like a hour or 2 then plug back in it turns on and is normal. So then i thought ok maybe the power supply....I buy and test 2 more power supply's problem happens again....Very rarely after i leave it off for a while i will get a warning That says Warning !!! The previous overclocking had failed. and system will restore its default settings. After seeing this I checked my video card settings and made sure i wasn't over clocking it but yet i still see that error very rarely. I could be overclocking my cpu but idk how to do that or even check if i am so i am not sure on that one i have completely wiped the pc and reloaded everything multiple times to see if that would help and it does for a few months but then randomly happens once or twice then goes away. My only thinking that could be causing a problem would be my mobo but is possible but my mobo is kinda old and if i replace it i have to replace my cpu for the most part since they dont make compatible cpus that fit. nor can i find a newer motherboard that will fit my cpu. SO i am not 100% sure if my mobo would be randomly shutting off my display but its and idea. I am just confused why its acting so weird and nothing i do solves it permanently so i am coming here after googling the problem and reading through 100s of forums with similar problems and trying what they did and yet problem persists. Any help would be appreciated.
Specs:
Cpu-Intel Core 2 Quad Q6600
Mobo-MSI ms-7380
Video Card i want to use-Amd Radeon hd 7700 series
Ram- 1x1g ddr2 crucial technology part# ct12864AA667.k8f
2x2g ddr2 corsair part #cm2x2048-6400c5
Windows 7 64 bit