Install Permission to Power users in XP

Hi
I am having a network of 200 computers. All my clients are member of windows 2003 Domain and all the users logon with their ADS username and password. My question is how can I allow permission to the users to install any application on their respective computers. Presently all of them are power users of their desktops and they can install only legacy application. Is there any way I can allow them to install whatever applications they want to without adding them to Administrator group. I am also using group policy to restrict few perimissions and rights. A reply to this question would of great help.

Thank you in advance

Umesh Kamath