Well, if you motherboard has an agp slot(as many integrated mobos lack graphics upgrade slots), you buy an agp card that's compatible(if your board has 8x agp get an 8x card), carefully install it(after reading it's directions of course), and then boot up. It should display using a generic windows driver, but look really low quality. If it doesn't display from the new card, you might have to enter the bios and setup the video options. Maybe select that your using an agp card instead of integrated or something like that, bioses vary. Then, you install the newest drivers for the card, like if it's nvidia based, dl the latest driver from nvida and install it.