To upgrade your computer's graphics card, unfortunately you can't just simply purchase a card and install it to your computer. Before purchasing a card, you must first confirm what is compatible with your motherboard. Graphics cards use either AGP or PCI Express technology. Many older computers use AGP. AGP cards can vary in version and bandwidth, whereas PCI Express cards can vary based on their lane size. Moreover, the card itself is not your only consideration when looking to upgrade your computer's graphics. You must also consider the strength of your computer's power supply as well, since most newer cards use a lot of power.
Download, install and run SiSoftware's Sandra (see link in Resources) to find out information on your motherboard. Click the "Mainboard Information" icon, then write down the information next to "Manufacturer" and "Model."
Navigate to the motherboard manufacturer's website. If you are not sure of the website's URL, enter the manufacturer's name into a search engine to find the company's website.
Go to the support page and enter your motherboard's model. Download the motherboard's manual or review the specifications.
Search the manual or specifications for "Expansion slot," "AGP" or "PCI Express." If the expansion slot uses AGP, note the version (AGP comes in 1.0, 2.0 and 3.0), as well as the bandwidth (1x, 2x, 4x or 8x). If the expansion slot uses PCI Express, note the amount of lanes (x1, x4, x8 or x16).
Search the manual or specifications for "Power," "PSU" or "Power Supply." Write down the power supply's voltage (3.3V, 5V or 12V) and amp rating (designated by "A"). Not all manufacturers list the amp rating in their documentation, so you may need to contact the manufacturer for more assistance.
Compare the graphics card you want to buy to the motherboard's expansion slot. AGP cards won't work in motherboards using PCI Express, and vice versa. Similarly, AGP 3.0 cards won't work in motherboards using AGP 1.0. A PCI Express x8 card will not fit in a PCI Express x1 slot.
Check the voltage and amperage of the video card to the voltage and amperage on your motherboard. A video card that requires a higher amp rating requires a powerful PSU.
Contact your motherboard's manufacturer or contact the graphics card manufacturer if you are not sure, even after comparing specifications, whether or not the card will work in your computer.