here is where you can download it.

go to this web

http://punkbuster.com/index.php?page=pbsetup.php

click on the WINDOWS, if you have windows and download it.
afterwards run it.
then add game, you have to pick cod 1 because there is no cod uo.
addgame and then start cod uo mp, and if it asks you for any changes click yes. turn the pb on in the multiplayers options. and hopefully it will work.

also make sure any antivirus program control lets it through so that it dont block it. or windows firewall.