Screen is blank (Happened many times before)

Registration date
Friday May 31, 2013
Last seen
May 31, 2013
Hello, so here is my problem, Basically each time when i mess with power on/off on PSU or unplug the PSU, something goes wrong with GPU, i have Sapphire Radeon 5770, and there is a blue light on side of it, it seems that it keeps restarting after roughly 3-5 seconds, the PC doesn't restart, the only thing that blinks is the gpu light, now I have had this problem many times before and I have no idea how I fixed it each time. Once i remember i just left it plugged in and came back after a while and it worked, now this time im trying the same, but in mean time im trying to find out if there is a real fix, the problem also consists of that earlier when I had this problem the motherboard built in GPU worked instead of PCI-E that i plugged in, basically if i unplugged the PCIE GPU then the motherboard GPU worked, but as I recall last time i disabled it in bios settings as I taught it would be a fix, but it wasnt (Clearly until this moment I dont know what the fix could be), I tried to reset CMOS by removing the battery and unplugging the PC, still didnt work, problem also is that I cant find either a button or jumper on my motherboard. Any ideas?