How to enable classic WINDOWS 7 theme?

Question

Windows

Hi all! Please help, I'm mastering WIN SERVER 2012 and in general the topic of domains, group policies, etc. At me the domain controller is lifted, users are created - everything works. I'm setting up a security policy and here's the plug ..
Disabled the ability to change themes, backgrounds, etc., but how can the user apply the classic theme by default? There is a point where you can specify the path to the theme that will be applied, but what is the path for the classic theme?