Computer not booting correctly??

[tolk]

I opened up my computer to move the audio cable that runs to the front of the machine (the graphics card EM was causing noise on the line). Was pretty careful not to touch anything, and didn't unplug or move anything else.

When I pugged everything back in and went to reboot, the computer started up and gets to the windows loading progress bar (though in a very low resolution version). After the progress bar completes the screen goes black as usual but then the monitor turns off (not receiving any output from graphics card) but the boot progress seems to continue as normal (eventually the windows startup sound plays).

Things I've tried:
Jiggling and re plugging the power cables etc.
Replacing the graphics card (with an old one, which wouldn't display anything).
Clearing the CMOS (both via BIOS and hard reset by removing battery for 5 mins).

I'm running out of ideas, is it likely the motherboard is fecked? Any other suggestions to fix it?

Computer Build:
E8400 3GHz Core 2 Duo
Gigabyte GA-EX48-DS4 Mobo
4GB Corsair XMS2
GTX670 Gigabyte graphics card

 

[tolk]

Update: Put graphics card in second PCI-E slot, computer booted, installed drivers for card, asked to restart. After restart I'm getting the same problem in the second slot.

Booted to ubuntu, which worked but it doesn't seem to be picking up the gfx card properly (would not let me change from the resolution 800x600 and seemed to think it was a laptop display??).

Not sure what the issue is, thought it was the mobo at first because I tried the second gfx card but now this is making me think its the gpu, any ideas, anyone??