I have tried everything that I can think of and almost given up hope, but first I will try to seek help.
Ill start from the beginning.
I unpacked my new Gigabyte 5870 slotted it into my gaming PC and powered her on. For a few seconds everything seemed to be working ok. The computer POST and displayed the normal mobo info and before It could get to the windows login screen the monitor went blank and the No signal popup appeared.
So I tried the usual.
Unplugging everything except the bare essentials. Reseated the Memory. Even held the power button in for 30 seconds. Reset the CMOS. Checked the power connection. But nothing seemed to work. The computer was Posting and I knew it was booting into windows like normal because I could hear the windows startup music. But for some reason there was nothing on the display anymore. So I stuck my old 8800GT back in and the computer booted up fine. No problems at all.
I then uninstalled the Nvidia driver. Updated the Mobo BIOS. Installed the ATI catalyst 10.6 drivers. "I have even tried v10.5 drivers" switched her off and put the 5870 back in and still no display. It cant be the cabling because the previous card works. I have also tried the 5870 card in another machine of mine and she boots up perfectly, no problems.
My only conclusion's I have come down to is my problem lies with either my power supply or a mobo incompatability issue.
I am running a coolermaster 600w SLI ready power supply and the box on the 5870 states 500w is the minimum. And from other forums I have read, that sort of psu wattage should be enough to power this card. So that just leaves the motherboard.
Someone please help. I dont want to end up buying a new psu, then still having problems and wasting more money on a new mobo.