Title.
We boot it up with the video card in, it beeps once like it should, but there's no display. Remove it and run off the motherboard's onboard, runs and displays with same number of beeps..

defective video card? if so I'll get something faster. I'm trying to get it to work though. The onboard isn't cut out for gaming..

Thanks.
need more info just ask. 4 Gigs of RAM and a 2.6 ghz dual core cpu.

and yes the onboard is turned off in the BIOS and within windows. it's not getting enough power. bad PCI slot maybe? the card worked in another computer, though.

Maybe an insufficient PSU? How much wattage does ir require vs. what it has?

are we talking about pci-e cards ,or older pci card

I'm meaning the power supply unit, maybe its not dealing enough power for the hardware you have. If you're going to troubleshoot the pci slot, try maybe inserting other pci, pci-express device and see if it works. :)

Older PCI slot and card.
Power supply gives 480 watts total. There was no requirements on the boxes.

Well, usually if you're gonna upgrade your system, you need to take in consideration the power the pc is currently using. When upgraded, the power supply must support the new hardware, so lets say your pc ran smoothly at 480, quoted from Nvidia "GeForce 8400 GS cards have a maximum power draw of 71 watts" so now you have to consider, if your computer used the whole 480w then you need to upgrade the Power supply.

Older PCI slot and card.
Power supply gives 480 watts total. There was no requirements on the boxes.

nvidia 8400 GS,is a pci-e card not a older pci card

http://www.bestbuy.com/site/BFG+-+NVIDIA+GeForce+8400+GS+512MB+DDR2+PCI+Graphics+Card/8990666.p?id=1218007087696&skuId=8990666&st=bfg%208400%20gs&cp=1&lp=2

PCI. the slot is PCI; doesn't have that tab to fit in the PCI-E. Also doesnt fit in the placement of the PCI-E slot on the motherboard.

ok yours is a BFG- with nvida chipset sorry ,
this nvida one says pci-e
http://www.nvidia.com/object/geforce_8400_Gs_faq.html

have you tried it all available pci slots ,im sure you have !

yes i have; only one slot will fit in on this motherboard.

Intel motherboard DG43GT. That's it.

Well, usually if you're gonna upgrade your system, you need to take in consideration the power the pc is currently using. When upgraded, the power supply must support the new hardware, so lets say your pc ran smoothly at 480, quoted from Nvidia "GeForce 8400 GS cards have a maximum power draw of 71 watts" so now you have to consider, if your computer used the whole 480w then you need to upgrade the Power supply.

Should be fine. My stock Dell 305w OEM PSU runs a (v. power hungry) Pentium 4, and a geforce 8600 fine. Then again, i know that some cheapass PSUs which claim to be 450w cannot power the same configuration.

The card works in other computers. But it might be a bad card. Or incompatible.

Course I double post.
It's incompatible for some reason. Other weaker cards work in that slot.
I noticed there are 2 thin pins sticking up at the top left of the card. What would they be for? No documentation came with it, only "plug, play, and update drivers."

I noticed there are 2 thin pins sticking up at the top left of the card. What would they be for?

Either fan or for a SLI-Bridge?

fan's already plugged in and dont use SLI so it's not that.