In case that User Account Control (UAC) is disabled, you can re-enable it to default settings doing the following steps.

IMPORTANT:
Once re-enabled UAC, you must restart the computer to apply the changes.

1. Open User Account Control Settings by clicking the  Start button (For Windows 7, 8.1 and 10).
2. Type uac in the search box (for Windows 7 & 10) or after the Metro interface appears, type uac (for Windows 8.1).
3. Select Change User Account Control Settings.
4. This will open the UAC settings interface.
   To turn on UAC, [1] move the slider to choose when you want to be notified and then
   [2] click on the OK button. Administrator permission required. If you’re prompted for an administrator password or confirmation, type the password or provide confirmation.

   IMPORTANT:
   Once re-enabled UAC, you must restart the computer to apply the changes.