Your graphics card "plugs" into the motherboard that you see fill the space when you open your case.
After you have removed the screw (or plastic clip) that secures the graphics card at the backplate of the graphics card (where you connect the monitor cable)
There maybe an "AGP lock" which is a plastic spring clip that hold the card in during computer transport.
This "AGP lock" is located where the graphics card "plugs" into the motherboard. It is at the opposite side of the AGP slot from the backplate (mentioned earlier).
http://www.newegg.com/Product/ShowImage...20ATX%20AMD%20Motherboard%20-%20Retail
Look at the plastic lock and try and determine if you have to press the lock up (towards the CPU) or down (towards the other PCI slots) to release the plastic spring clip.
Looking at the picture I linked to I believe you will have to lift up the plastic lock.
VERY IMPORTANT!!! Simultaneously you will pull the Graphics card out of the AGP slot. Once the card is pulled out of the AGP slot you can pull the card out of the computer fully.
http://www.newegg.com/Product/ShowImage...GP%204X/8X%20Video%20Card%20-%20Retail
In this image you can see the part of the graphics card which is "latched" onto by the AGP plastic lock clip. It is the upside down plastic L shape that resides next to the AGP connectors that plug into the motherboard. This is where the locking clip on the motherboard will hold the AGP card.
As far as accessing the clip I would use a plastic bic (writing) pen and place it below the graphics card but resting on the heatsink of the nForce3 chipset and (using my right hand)use leverage to lift the plastic spring clip up (towards the CPU). This should require VERY Minimul effort. You do not want to damage the heatsink of your chipset. Once the clip is lifted I would simultaneously take my left hand (once the clip is pressed up & held up) to pull the graphics card straight out away from the AGP slot.
I hope this helps.
Note: I have never used or owned this motherboard and looking at the image it appears as though DFI really made that clip without much thought to removing the graphics card. But I hear it's a great board
😀