System won't power up with Video Card installed

I tried to build a new system:

New Components:
-Asus P5N-E SLI Socket 775 Motherboard
-Intel Quad Core Kentsfield 2.4Ghz Q6600 CPU
-OCZ Platinum Rev 2 2048MB PC6400 DDR2 800MHz x2
-BFG Tech 650W PSU
-Thermaltake V1 CPU Cooler for AMD and Intel CPU

Old Components:
- BFG GeForce 7900 GT/GTO 256MB

Here is my problem (please bare with me, English is my second language):

After installing all the components into the case I tried to power up the system but it would not power up (CPU fan came on for a split second though) but the LED on the mobo would always be lit.

I took everything apart again and checked the CPU and mobo for any damage but could not find any, reinstalled everything (making sure that the thermal paste between CPU and heat sink was correctly applied) nothing had changed. First I thought it might be due to faulty RAM and took out all but 1 stick then switched between the 4 sticks I have and changed the slots it was in, no change.

Now when I take out my video card completely the system seems to boot up fine, except for the 1 long 2 short beeps that, if I remember correctly, mean there is a problem with the video card.

I searched many different help boards for a solution to this problem but couldn't even find anybody with the same issue. Having looked at many different sites I was under the impression that tomshardware.com has a very competent community and I ask your advice.

Thank you very much!

EDIT: The Video Card is working fine in my old system.

Thank you for the reply.

I tried an old Radeon card I had lying around with the same results. The power supply is firmly connected (the PSU has 2 PCIE cables and I switched em as well), I do have a feeling it might be something simple as that which I am overlooking (I hope).

I

Yeah tried another one

Ultra 600w X-Finity Power Supply w/2 80mm / Titan

No change

Are your reset and power button LED connectors plugged securely and properly into the motherboard? Double check. That happened to me recently as I was reassembling my computer. Dang plugs were connected backwards.

You could try a bare setup.

Unplug the HDD(s), optical drive(s), floppy (if you have one), and add-on sound card (if you have one). The only hardware that should be plugged into the board should be 1 stick of memory, the cpu, and your geforce card (although you may want to try the same setup with your radeon card.)

If it still doesn't power up even with that minimum of equipment installed then I'd be inclined to say that it's you MB that's at fault and that you should look into getting it exchanged. Especially since 1) your geforce card still works and 2) your system won't boot with something plugged into the primary PCIe x16 slot.

One other thought though. If you can get your hands on one you may want to see if you can try out a PCI video card. If it boots up that way then I'm almost sure that it's your primary PCIe x16 slot that's at fault which would of course mean getting your MB replaced.

I really appreciate you all trying to help me out here

I am, in fact, trying to fire it up "barebone", checked the PCIE slots (seem to be clean) and reset the CMOS (switched jumper, took out battery and unplugged PSU for a minute).

The mobo is SLI ready and has two PCIE slots which I have tried, as I said before I am afraid I might have messed up on something obvious. Unfortunately I don't have a regular PCI card that I could use and the mobo does not have on board video.

I will do some more research and definitely let you all know the results even if it means I need a new mobo.