This is some sort of anticheating software that you can’t really remove called “Punkbuster”:http://www.evenbalance.com/index.php
For those who want to really uninstall Punkbuster, the file PnkbstrA.exe is located in the Windows\System32 folder in Windows XP. Before deleting it, go to Start Menu -> Run -> type msconfig, then look at the Services tab. Uncheck PnkbstrA, and delete the file. That should get rid of the thing.
Apparently some online servers require Punkbuster to be installed, but there is an uninstall program you can download if you don’t like hacking with msconfig:
To manually install/uninstall the components, users may use our PBSVC Setup Program. However, uninstalling the new service components will disable PunkBuster and may prevent playing on PunkBuster servers.