"Overclocking, Unreal Tournament is sensitive to overclocking, if your system is overclocked & you have problems running Unreal Tournament, e.g. lockups during the game, try restoring the machine or video card to its default speed, or applying more cooling.
Install DirectX 8 you need it to use Direct3D & other features. DirectX 8 has also been shown to improve frame rates quite nicely in Direct3D mode too.
Patch it; get the latest patch for Unreal Tournament, currently that is 436, available for Windows 9x/Me/NT/2000 here, Linux here & Mac here. This will ensure you have the most current version of the game & all the included fixes/optimizations as a result."