Best idea would have been to upgrade to Linux
I don't know much about COD, but if it is an online game, could you use firewall/router settings to block the ports?
I believe there are some tools for XP that will allow you to do this remotely on all workstations, or for particular user accounts.
Policies can be used to disable removable media.
I know that they don't work on some of my customer's machines.
Disabling the USB ports in bios and password protecting it, disconnecting the front ports, filling them with glue, or using a pair of pliers to make them unusable, are some of the tactics I have seen my customers use to prevent this sort of thing. Of course that means that it is more awkward for you to use them, but you could do it on the most vulnerable ones.
Maybe someone should come up with a USB port lock?
Flash drives are fast becoming a real nuisance on networks, data theft and virus infection are real concerns for companies.
The sig between the asterisks is so cool that only REALLY COOL people can even see it!