What is a Power User in Windows

A member of the Power Users group may be able to gain additional rights and permissions on your computer, and may be able to gain complete administrative credentials. A member of the Power Users group may also be able to expose your computer to other security risks, such as running a virus or running a Trojan horse program.

By default, the rights and permissions that are granted to the Power Users group include those rights and permissions that are required to allow members of the Power Users group to modify computer-wide settings, to install drivers, and to run (or install) non-certified programs. For example, a member of the Power Users group could install a malicious program or a DLL, and then cause the administrator or a system service to run the malicious program or the DLL. By using this technique or other techniques, the member of the Power Users group may be able to gain additional rights and permissions on your computer, including complete administrative credentials.

To help prevent this problem, use these methods: 
Do not use the Power Users group.
Deploy certified Microsoft Windows 2000 or Microsoft Windows Server 2003 programs in your enterprise. Programs that are certified for Windows 2000 or Windows Server 2003 are written to avoid requiring unnecessary access or administrator-level credentials.

The Power Users group is a built-in local group that primarily provides backward compatibility for running non-certified (or "legacy") programs. However, members of the Power Users group can also change COM object registrations, change file associations, change Start menu shortcuts, and install drivers for hardware devices. For additional information about the default rights and permissions that are granted to members of the Power Users group, visit the following Microsoft Web sites.