Eating foot...
Well sorry about that. Wasn't sure either way. But you don't know for sure what actual graphics chip it is? Is it AGP 2X? 4X? Where is your post about the specific system you are referring to? I did not see it. The best cards I've used and read used for UT are the ATI Radeon and GeForce 2 GTS. I have personally used both and am currently using the GeForce as it has more horsepower overall and I believe will be more widely supported over a broader range of games. I am very picky about my fast paced games such as Half-Life, UT, Oni, etc. I like precise, fluid, responsive movement and when I tried the integrated Intel chipset on a 1GHz P3 system it was OK but not great. I don't know for sure how well yours will be but I would say probably decent. It may well outperform the Intel chip simply because of the higher motherboard FSB. Are you using a DDR Athlon or original? Original will have 200Mhz FSB while the former will be 400.
Unless you simply don't have any cash I'd ignore the built-in chip and buy a separate card. I think you'll have a better gaming experience because of it. You can get very good cards for under $200 these days in fact probably closer to $150.