Disable Adhoc networking

Since deploying SP2 to our XP notebooks, our engineering department finds
it fun to create their own adhoc networks for file sharing, etc. Of course
they could care less about the security aspects of their actions, so our
only recourse is to find a way to disable the adhoc networking capability.

Easy enough to remove the Wireless Network Setup Wizard from the control
panel, but how can I remove it from the "My Network Places" dialog and the
"Choose a wireless network" dialog? Group Policy would be the best answer,
but I have not as yet been able to find any solution.

Thanks in advance - perhaps there's another approach I'm missing? Any
guidance is appreciated.

JonnyB