Remove software install privilege from Power Users Group

[S.G]

I currently run a Small Business 2000 Server network with
Windows XP workstations.
I currently have a legacy system that requires each user
to be a part of the local Power Users Group for proper use.

I do not want my users to be able to install any type of
software on the local machine.
How can I remove that right from the Power Users group???

Help community...

Sebastien