XP Power users can’t install apps

I’m setting up new xp computers and I have added the domain users to the local power group. Most of the time then can install programs but sometimes they get the you need admin rights to install this software and that creates problems. I want them to have access to install any app, but have the power users template. I may be asking too much but it is good that under the power user’s template they can’t change network settings etc. Any help would be appreciated.