Help! Graphic card not working

I just bought a GeForce 8400GS yesterday but after slotting in the card, my monitor won't display anything! I've made sure to connect the monitor cable into the VGA slot, as well as ensuring the card properly fitted. The power LED on my PC lights up (non-blinking) but that's about it. I'm guessing there isn't enough power with my standard power supply unit (230 VAC) but I could be wrong, so before buying a new PSU I might as well ask for opinions.

The motherboard I'm using is ASUS P5GZ-MX, and this VGA card is the only modification so far. Also, according to the ASUS site, there are 2 PCI slots, 1 PCI-E x1 slot, and 1 PCI-E x16 slot. I only see two PCI slots and a black slot, which PCI-E is the black slot and where is the other one suppose to be?

You need to go in the Bios and disable onboard Graphics and enable PCI-Express (PEG) Graphics.
Tell us how many amps you have on the 12v rails on the PSU and list your specs also.

Your new card will not work until you do as evongugg says, THEN plug the monitor into the new card.

OK, the 230VAC means youre running 230 volts AC. That means your power supply is connected to a 220 volt outlet. It has nothing to do with the output of the psu. I dont think the 8400 needs another connector (power connector on the card) so Im guessing your power is OK. Pull out your video card, then go into your bios, then select pci-e. Also, is your connectors from the card all the same as you had before? DVI etc? Also, your pci slot is usually the longest one. Did you download/install the drivers correctly? And also, being that you had onboard graphics before, did you erase your old drivers? Its ok to do so, as the windows drivers will still make everything work. If you dont erase your old drivers, they could cause problems, especially if youre using something other than nVidia for your integrated video (Intel/ATI). While in your case, pull out your power supply and check on the side or back, thats where youll find how much power your psu actually outputs

Maybe this might have something to do with it ?

1 x PCI-E x16 @ x4 speed

This is from your provided link:
1 x PCI-E x16 @ x4 speed
1 x PCI-E x1
2 x PCI 2.2

I asked since the PCI-E x 16 slot is only 4x instead of the normal 16x would that be your issue?

I looked it up als 4X for the PCI-E slot, but even so at 4X it should work, just be a lil slower. According to the pic of the mobo, the black is the correct slot. Ill ask again, have you deleted your old drivers? and have you installed your new drivers? Pull out your card and try it without so you can go into windows, then make sure pci is active in bios

Hook up the monitor to the integrated video port. The go into the Bios and change the video from onboard to PEG (PCI-Express). Save the Bios and exit. The screen will turn black. Turn the computer off. Connect the monitor to the PCI-Express card and you should be fine.

In the BIOS menu, the options for Booting Graphic Adapter Priority are [Internal VGA] and [PCI/Int-VGA]. I chose the latter one, so after doing so, the screen doesn't turn black. It's still displaying normally. Then upon inserting this card, the monitor doesn't display anything, regardless of where I plug the monitor. After removing the card, the setting is back to [Internal VGA].

@jaydeejohn: I do have the installer disc, and I know the drivers are different, but there should be any conflict if I use an nVidia card for an integrated Intel, right? Also, isn't the driver supposed to be installed after the card is fitted?

hey can you explain how the fix your problem because a have the same one...