Mobo / CPU / PSU broken ? OC

Hey I OC'd my CPU ( AMD 955) on my Gigabyte GA-MA-770-UD3 i had it at 3.5 Ghz and had it running for weeks before,so after a while i set it back to stock settings cus i didN't need the OC and then after a while I set it up to 3.5 again.Thats when my PC didn't work anymore.The PC powers up but there's no beep, The graphicscard's light blinks every 3 seconds or so and the gpu fans keep roaring up everytime the light blinks (so like the pc is booting all the time), I dont get a picture on my screen,its not the gpu cus i tested that in a different PC.I tried booting without my 8 GB of RAM but still the same and i also cleared the CMOS.Now my question is : How can I find out which component is broken?

BTW my PSU is a cheap 500 W one but it still had some good reviews and it has only a 4pin Mobo connector ( my mobo has an 8pin ) but this worked fine always(the 4 pin in the 8 pin).

Thanx