They can also remove users from the Power Users, Users, and Guests groups. They can create local groups and remove users from local groups they have created.

Members of the Power Users group can create user accounts, but can modify and delete only those accounts they create. They can also log on to and shut down the computer, but they cannot change security settings. Members of the Backup Operators group can back up and restore files on the computer, regardless of any permissions that protect those files. Members of the Administrators group have the largest amount of default permissions and the ability to change their own permissions. Belonging to a group gives a user rights and abilities to perform various tasks on the computer. The built-in groups are created automatically when you install Windows 2000 or Windows XP.

Groups displays all built-in groups as well as groups you create. The Power Users Group is built-in, with all the permissions, etc. One doesn't add a group called Power Users. I can change the time, I can install many applications, I can do all the things that a Power User can do. I'm replying to you from a Power User account (which shows up as 'Unknown account type' in Control Panel > Users. Click to expand.Sorry, but it does indeed work.

Windows power user tools