Using Netplwiz is a useful tool for managing user accounts in Windows 10, 8 and 7. Here's how to make standard user an administrator using the Netplwiz utility:
- Press the Windows key + R key at the same time to open the Run box. Type netplwiz and press Enter.
- Check the "Users must enter a user name and password to use this computer" box, select the user name that you want to change the account type of, and click on Properties.
- Click on the Group Membership tab. Click to check the Administrator radio button and click OK
- Close the advanced User Accounts (netplwiz) window.
http://www.top-password.com/knowledge/change-standard-user-to-administrator.html