Epic Games posted up a tweak guide for all Unreal Tournament 2003 fans.. Here is a clip from it:

This guide provides an overview of how to get the best possible performance out of UT2003, when you have patched the game to version 2186 or higher. When tweaking performance, its best to start from the default settings which were set based on your system configuration when you first installed UT2003. To return to the default settings, delete your UT2003.ini file (in your UT2003system) directory, and start the game.
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