No signal to monitor - what could be the problem?

[kantastisk]

I've recently put together a pc for the first time. When I boot it up I don't get a signal to the monitor!

specs:

motherboard: msi k9a2 platinum
cpu: amd athlon 64 x2 6400
cpu cooler: Zalman 9500A
gpu: Sapphire Radeon hd 3870 X2 (two gpu's in one card)
psu: ocz gamexstream 700 watt
ram: 2 x Kingston HyperX, 800MHz 2GB
HD1: WD Raptor 10K rpm SATA 2
HD2: WD 7,2K rpm SATA 2

On the back of my gpu are to dvi ports. I've tried dvi-hdmi and dvi-svga adaptors on an lcd I know to be working and dvi-svga on a crt I also know to be working.
I remembered to connect two 6-pin power connectors externally, and the card is in a pci-e x16 slot on my motherboard.
When I boot up my pc I see lights going on on the motherboard and the gpu and all fans are running with no weird noises or anything. -Only weird thing is the gpu fan sounds like it's running at max speed. No signal though.

SO - I had the store test the card, and they say they're getting a signal on a 1kw psu. But shouldn't my card be working with the ocz 700w?? Googling it shows me that others have this setup working.

Please note that this computer is brand new and has no OS installed so there's a risk I might have messed something up while putting it together. What could be my problem?

[Alaron]

Welcome to PCMech.

Try this procedure (follow it carefully) and let us know the results:http://forum.pcmech.com/showthread.php?t=132409