What does the Windows 7 local group Power Users actually do?

Solution 1:

You're correct, the Power Users group does not do anything at all in Windows Vista and later.

From http://technet.microsoft.com/en-us/library/cc771990.aspx:

By default, members of this group have no more user rights or permissions than a standard user account. The Power Users group in previous versions of Windows was designed to give users specific administrator rights and permissions to perform common system tasks. In this version of Windows, standard user accounts inherently have the ability to perform most common configuration tasks, such as changing time zones. For legacy applications that require the same Power User rights and permissions that were present in previous versions of Windows, administrators can apply a security template that enables the Power Users group to assume the same rights and permissions that were present in previous versions of Windows.

Solution 2:

Not quite true - if you use Office 2016/O365, all macros are disabled until you are at least a power user. You can enable anything you like and there is no error - it just doesn't work. But after I upgraded myself to the Power Users group (I had already enabled the right options in Trust Center), I can record, write, or run vba solutions as I do when logged in with my administrator account.

Caveat: This was tested in a Windows 7 environment with O365 only for Outlook, so I can't swear it will work for the other apps, but VBA permissions have never varied per-application before, so I'm assuming it will be the same for the Excel, Word, and PowerPoint macros.

Solution 3:

Power Users also allows an account to create shares. I tested it by creating shares in a cluster with new-smbshare command where I only added the domain account to Power Users. Without being in Power Users, the domain account could not create the share. Useful if you do not want to make an account an Admin just to be able to create shares.