hello and welcome to techspot
the first thing i would do to install a viedo card is to uninstall all of your old drivers, then lokate a free pci, pcie, or agp slot which ever you have, and take the old card out or if there isnt one in just install iit, plug the mointor into it and then turn the computer on, insert the cd that came with youer veido card and load them, good luck
REMBER TO UNPLUG THE COMPUTER BEFORE OPENIING IT, faliure to do so could result in injury or damge to parts