If you want to turn off a wireless card, you could go to Start->Settings->System->Power->Wireless and pick "wireless signals off".
This is in WM2003, have no idea if it's possible in WM2002.
But if you want to disable a program that is running for your Wireless card, try PHM Task Manager (
http://www.phm.lu/products/PocketPC/taskmgr.asp) and end the process from there.
I have no idea if this helps :)