Answers

1. Log in to the PC as an administrator (domain administrator)
2. Go to "Control Panel|User Accounts"
3. Go to "Manage User Accounts", then the "Advanced" Tab
4. Click on the "Advanced" button in the middle of the form
5. Open the "Groups" folder, then double-click on the "Administrators" group.
6. Click "Add", then add the relevant user (Username@Domain)
7. OK (etc) to close all the windows .
8. Log off the admin account, then log in to the domain user and test.

http://social.technet.microsoft.com/Forums/windows/en-US/f55d41-4713-a99d-62d67ed88595/adding-a-domain-user-to-the-admin-role-within-the-local-user-management-breaks-all-metro-apps-for?forum=w8itproinstall