Hello there, I bought a new graphics card (Radeon HD7770) and PSU (Corsair CX500M). After installing I plugged my PC back in but the screen stayed black (no signal whatsoever). I checked whether all cables were connected properly, and tried again, no change. Then I got a different monitor and switched from HDMI to VGA, still no improvement. So I put the old PSU and graphics card in thinking I need to install it first, but now the screen stays black on the old PSU and Graphics card. I tried with no graphics card and connected to the inbuilt VGA connection (on motherboard), but still nothing. I have tried to reboot bios by taking out the battery and additional memory, but still nothing. I now have the new PSU and Graphics card in the PC, and have tried every cable connection possible. I turned on the PC with the 4-pin CPU power cable plugged out one time to see if it made any difference, and it sounded different (though all the fans were working). I am at the end of my knowledge and could use some help. Is it the PSU, the Graphics card, the Motherboard, something else?