There is a free Linux distrubution that contains Unreal Tournament 2K3 demo in it. You just put cd in your CD-Rom drive and watch Linux operating system loads itself , then UT 2K3 demo.
You can download that distribution from link below, or you can visit official site. After you download image file, you have to burn it on a CD-R, then boot your computer with that cd.

(You may need to change your computer's boot sequence on your bios in order to cd boot, if you don't know much about this stuff ask a friend who knows )

ISO binary file here

Official Gentoo Linux site here.