graphics card

Go back into your BIOS setup and there will be several menu headings. It's probably under 'Chip configuration' or something like that.
You are looking for 'Onboard VGA or Video'

Disable it, then exit via 'esc' key and remember to say yes to save your changes.

Also, you should go and get the latest version of the Nvidia graphics driver.

http://www.nvidia.com/page/support.html

Download the complete installer package for your version of Windows.

When you do boot it up with the new card, you will get the 'Windows has found new hardware message'

Just cancel out of that and then go to wherever you put your nvidia downloaded driver package and double click it.

yes but once i put the new card into my system, the computer wont display anything on the monitor even if it is still plugged in to the old video card

Is it an AGP video card?

If you take it out of the computer does your onboard video work properly?

Make sure you disable the onboard VGA. (sometimes when you put an AGP card in, the BIOS will automatically disable the onboard VGA)

When you insert the card in the AGP slot, make sure it is pushed right down as far as it will go. These cards are finicky that way.

If you have got the onboard disabled and you are getting no signal to the monitor from the new card, then it probably is poorly seated card, bad connection somewhere, or possibly a bad card.

I cant find the "onboard VGA" heading under any of the sub-menus. I was in AMIBIOS setup then went under the heading PCI / Plug and Play Setup and found these options, but what should they be so i can use the new AGP card.

Plug and Play Aware: Yes
Primary graphics adapter: PCI
Allocate IRQ to PCI VGA: No

It should read like this:

Plug and Play Aware: No
Primary graphics adapter: AGP
Allocate IRQ to PCI VGA: Yes

try that,

and did you check to make sure the AGP card is seated properly. Take it out and put it back in and push it right down as far as it will go.