You know, I've just remembered you don't have to!
If you uninstall ALL network cards, Windows automatically removes TCP/IP, as there is nothing left to bind it to.
To remove TCP/IP manually (without removing the card), just go to the NIC Properties and remove the protocol. As I recall, if you remove the only protocol it will also remove any clients and services that depend on it (e.g. Client for MS Networks, File and Printer Sharing).
SD