Graphics card stopped outputting to monitors

[Guest]

Hey guys, I was wondering if you would be able to shed any light on my current crisis.
[Current system hardware - 8GB OCZ Platinum DDR2 RAM (800MHZ), Gigabyte GA-EP35C-DS3R Motherboard, Intel 8400 3GHZ Processor, OCZ Pro XStream 1000 Watt PSU, Samsung Spinpoint f1 1TB harddrive, and then the original graphics card was a Nvidia 8800 GTX, and the new card is a ATI Radeon HD 5770)
I've been running my desktop PC for a couple years now, and upgraded bits and pieces, and have had it working solidly for the past couple months. About a week ago it started to have pixels distort, strips of them change colour, polygons not render correctly on screen, BSoD's etc so I decided it was either the graphics card or the drivers for it causing the issues, I assumed having it been the only thing to have remained from my original system it was just getting old, so I attempted to fix the drivers and upon one reboot the whole thing stopped working, the PC would load fine, the OS would boot up and I would hear the start-up sounds and things from Windows, but nothing outputted to my screens.
I then got an old Nvidia 7900 I had laying around and tested it in my system to check it was the graphics card, It only had one DVI output (I use two 22" screens) so I only used one screen and turned it on, and the computer worked just fine, source was outputted to the monitor and I could use it. I then took out the 7900 and ordered a new 5770, and upon installing it I get the same problem as my original GFX card, the fan spins, proving it is getting power, but nothing is outputted to the screen as if this card is also faulty, but I know there is nothing wrong with this card for a fact.
I thought I may have just exceeded my maximum RAM allowance for the Motherboard as the new card is 1GB internal and the old 8800 was only 768MB, so I removed a couple RAM sticks and tried rebooting but that also didn't work.
I really am lost as to what the problem could be because the only other item that I assume could have gone wrong to cause this would be the Motherboard, yet it was able to use the 7900 just fine.
If you've got any ideas or can give any help I would be very greatfull.
Cheers

 

[borisof007]

When you installed your new video card, did you COMPLETELY remove your old drivers via Guru3d's Driver Sweeper?

I doubt you have a card that's DoA (although it could be a possibility) but most likely I would venture a guess that you left your old nvidia drivers on there and they're conflicting

 

[Guest]

Update: I realised the 7900 required no extra power yet my 8800GTX needed two 6pin power inputs, and the ATI 5770 requires one 6pin plug. I've tested to see if it was a rail causing issues so switched to using different 6pin connecters, I even converted two molex plugs into a 6pin plug with the adapter supplied with the graphics card but still it's had no effect. Anyone at all got any ideas?

 

[Guest]

@boris, none of the drivers are removed because the 8800GTX stopped functioning before I could play with them, but surely the drivers are mainly bound to the OS so even if they do conflict at least the BIOS should post?

 

[borisof007]

Ah, so I mistook your problem, you can't even post with the video card installed?

I would definitely say that it's your video card that's DoA. RMA it for another.

 

[Guest]

Nope, both the 8800GTX and the ATI Radeon 5770 won't allow a post, they display nothing at all, even though the computer itself functions as normal. The 7900 would do everything except obviously the dual screens as it only has one DVI out. The problem is the 5770 I bought off a friend who had it running in a previous system just before I got it... so I'm pretty sure it works, but not positive having never seen it run myself

 

[Guest]

Update: just ran the 5770 in a whole new system that was working fine with its original GFX card, and it caused the same issue, windows loading but nothing outputted to the screen. After putting the original card back in it continued with that problem and I had to remove the CMOS battery and default it to get the original GFX card from that system working and outputting again. I'm still totally lost as to why the card is able to interfere with the original card, and if the 5770 is just DoA or the original problem caused by the 8800GTX has interfered with the 5770 so it acts similarly.
Anyone with any ideas / other questions / thoughts on the matter please post them as this is driving me mad