I had (before i upgraded) virtually the same system albiet with 256Mb of RAM and a Ti200. It could cope with anything until Tourney 2003 came along... now its a 1800+ XP with 256Mb DDR and new mobo and the Ti200 runs at 250/535 (faster than your Ti500!) and now its copes with UT2003 at max settings at 1024x768 with NO major slowdowns! I upgraded to this for just £143 (about $210) for memory (PC2100), CPU, 2600+ Fan/Heatsink and ECS K7S5A Mobo. I f I was you, upgrade that CPU 1st as that is whats holding your GF3 back. For example, on my ol' Duron 700, I got just 4359 3DMarks on 2001SE, now i get nearly 8600! Just make sure your board supports a CPU faster than 1Ghz. If its an Athlon, you would get 1.4Ghz max on a 200 bus, if it's a 266 bus you better check the BIOS updates to see if it supports the XP's. If it's a PIII then your buggered unfortnately, as you couldn't get past 1Ghz. But, hey back to the question! YES IT WILL RUN RTCW and even MOH:AA on Omaha (might struggle, but do that upgrade and it flies!)
Hope I answered your question!
sorry, forget the ramble about the PIII, you do have a AMD! Oops.