In order for us to be able to offer advice for a new video card, we need to know what power supply you have.

If you could take a look inside the computer to find the make and model, and then provide a link to it.

If you can not find a link, then we need to know wattage and amps for 3.3V, 5V and 12V which you can find on a label on the side of the PSU.