These next steps will guide you to correctly installing the graphics card in your computer.
Remove all the cables, including the power cables before opening the unit.
Lift the tab to unlock the side panel.
Remove the air deflector (the clear plastic cover) by pulling on the handle.
Locate the graphics card in the desktop.
Using a Phillips # 1 screw driver, unscrew the screw right next to the graphics card.
Last thing to do is to gently shake the card out of it's slot by pulling it straight out. (If the card does not come out easily, don't force it. You need to release a latch on the logic board behind the AGP connector while pulling out the video card.)