I have got a question to ask.  If one of the computers I use has 1GB of RAM, would it make any performance difference to upgrade to a 512MB PCI video card?It'll help in video department (using graphic programs, playing games, watching video, etc.).if you upgrade RAM you will find running more than one application will be much smother, like for instance if you were playing a game and you wanted to Alt + Tab out; to put some music on or look something up on the internet, higher RAM would make this process much QUICKER. i generally found Alt + Tabbing out of a game with 1Gbs of RAM is very slow and i would recommend getting 2Gbs to speed things up.

if you upgrade your video card you will see an in game FPS increase and you be able to put your display settings higher without decreasing performance.

and if you don't play games then getting a new video card seems kinda pointless  mannsupreme, I would have to say that the computer that I want to upgrade the graphics card on has a maximum of 1GB of RAM, and can't support any more than that.  However, I haven't upgraded the video card of our library computer, and am adding even more RAM to it right now.  Speaking of our library computer, it has 2GB of RAM, and will have 4GB of RAM when I upgrade.  However, as the installation of Windows XP on the library computer is 32-bit, only 3.25GB of RAM will be detected.  That won't bother me any.

The computer that has 1GB of RAM is a Dell that is in our basement, which I upgraded last year.  I was thinking of getting a better video card as Doom 3 has a choppy framerate when played on the Dell in higher resolutions.oh ok then, what video card does you current Dell system have? i just checked the requirements for Doom 3 and i would suggest getting a 128Mb video card or a 256Mb video card if you want smother game play. what dell system is it? because its quite unusual for a dell system to not accept any RAM larger than 1Gb or are you using a laptop?
but to be honest the game should run fine without a RAM upgrade  The Dell I'm using is a desktop computer from 2003.  I'm not trying to upgrade the RAM, as it is maxed out.  It currently has a 256MB video card installed, and I am thinking about upgrading to a 512MB video card.  As the computer will only accept PCI cards, I know of only one card I can get.what dell system are you using? and what card are you thinking of getting?The computer is a Dell Dimension 2350 2.4 Ghz with Windows XP Home Edition.  The video card I'm trying to find is the NVIDIA GeForce 8400 512MB PCI.  (I believe I've seen that card on eBay.)From what I know, there's two versions of that card, PCI and PCI-E. 

For instance, here's a link to an eBay listing of the PCI card.  The PCI-E card is far more common.

http://cgi.ebay.com/EVGA-512-P1-N724-LR-GeForce-8400-GS-512MB-DDR2-PCI-Grap_W0QQitemZ290293508581QQcmdZViewItemQQptZPCC_Video_TV_Cardsi found the card you are looking at on the EVGA website you might want to take a look at it
http://www.evga.com/products/moreInfo.asp?pn=512-P1-N724-LR&family=GeForce%208%20Series%20Family
they are the same card but im just showing you this if the card on ebay is bought outI just looked and NOTICED that this card requires a minimum 350 watt power SUPPLY, and the power supply in the system is a 300 watt, which I had installed last year.  I cannot buy this card unless I upgrade to a better power supply.  I'd need to see the maximum wattage the computer is able to use before continuing.Speaking of which, this would be the PSU I'd want to get:

http://pcpowerzone.com/2350.html

Anyways, I'm going to wait for a while before upgrading.hmm that's a shame because there are much cheaper and better PSUs around but your system doesn't support a standard PSU but it looks like that would support it. if i find a cheaper power supply ill let you know