Unreal Tournament III PC System Requirements Revealed
It should come as no surprise that UT3 will require a modern machine for it to run. UT3 will barely run on a 2GHz single-core CPU with 512MB RAM and an NVIDIA 6200+ or ATI Radeon 9600+ video card. For better results, the recommended specs call for a 2.4GHz dual-core, 1GB RAM and an NVIDIA 7800GTX+ or ATI x1300+ video card.

http://kotaku.com/gaming/pc/unreal-tournament-3-pc-specs-306546.php