7800gtx blank screen on boot problem

[pegasus1]

Tricky one this. Hardware is as follows

Mobo A8V-VM SE
CPU SD 3700
GFX 7800GTX 256
latest and correct bios and drivers for all hardware.
XP fully patched
All are at stock with 2x512 Ram connecting to an Analogue 17" monitor.

Its a new build and all components worked fine in a previous build.
The rig runs fine using the OB graphics, i booted into the Bios with the 7800gtx instaled, i changed the bios gfx setting from OB VGA to PCIE VGA.
I shut down and connected the monotor to the 7800 using a DVI to VGA adapter.
When i boot up the monitor comes on but i get a black screen there is hardrive activity and the fan on the 7800 is spinning but not at full power.

If i boot with the 7800 instaled but using the OB gfx then the 7800 fan runs at full speed.

I cant test the 7800 and adaptor until i get back to work later today (in the rig in spec) and i cant try another PCIE card or another adaptor in this rig until next weekend.

As i cant rule any component out at the moment i see three possibilities.
1 7800gtx broken (all ive done since it was last used is removed the WCing block and refitted the air cooler)
2 DVI-VGA adaptor broken
3 Mobo PCIE slot broken
Does anybody have any suggestions or comments.

 

[Sir Random]

Did you uninstall the OB gfx drivers before installing the NV drivers?

How did you switch back to the OB gfx if the screen was blank?

 

[pegasus1]

Did you uninstall the OB gfx drivers before installing the NV drivers?

It was happening before i installed the OB drivers and after, i dont think the OB drivers are an issue as it goes blank straight from boot. turn on PC, Monitor makes that pinging sound, green light comes on, black screen, this makes me think maybe the adapter is iffy maybe.

How did you switch back to the OB gfx if the screen was blank

Turn off the machine, remove the 7800gtx, plug monitor into the mobo vga and boot up.