Before opening the case, unplug the PC to avoid an electrical shock hazard. Exercise caution as there are sharp edges on a PC and its components. Always wear a static electricity discharge strap and attach the lead to the metal frame of the case, when working with your PC's components to avoid damaging your PC. Note that some manufacturers will void your PC's warranty if you open the case.
It is wise to start by changing your current video resolution down to the minimum settings of 16 color, 800 x 600 dpi and set the refresh rate to "default". These changes are made in the Display section of the Windows Control panel. After saving these changes, shut down Windows and unplug your PC.
Identify the slot you will use for the graphics card. In most cases it will the the larger (AGP) slot closest tot the CPU
Remove the cover plate adjacent to the slot for your graphics adapter card
Align the card over the slot with the video connection facing toward the outside of the PC
Set the card into the slot and press down firmly. Make sure the mounting bracket is properly aligned with any slot that might be present. It may be necessary to gently rock the card from end to end to secure it in the slot. The gold contacts at the bottom of the card should nearly or completely disappear into the slot. The card should be level and straight.
Secure the graphics adapter mounting bracket to the case with a screw (or replace the securing mechanism your case uses.
Replace the cover
Plug in the PC
Connect the video connector from your monitor to the connector on the graphics card
That completes the hardware installation, next you will need to start the computer and complete the software installation. Your graphics adapter should have come with a disk which contains the appropriate drivers.
Follow the manufacturer's instructions for installing the software. Windows will detect the graphics adapter and start the hardware wizard; simply follow the prompts. Some manufacturers require you to cancel the hardware wizard and complete the installation using their own installation instructions.
After everything is working, you can go back into the Windows Control Panel and reset the resolution and refresh as recommended by the manufacturer of your monitor. Failure to use recommended settings can result in damage to your monitor.