Yes button grayed out in UAC prompt - Solution

If the UAC prompt window asks for administrator password when you try to install a software etc, and the Yes button is disabled, you might have lost administrative privileges on your user account. Here's how you can restore them.

1. Press the Windows key + S combination on your keyboard to open the Windows Search bar.
2. Type recovery to open the Recovery Options. 
3. Under the Advanced Startup section, click the Restart now button.
4. Under Choose an option, click on Troubleshoot.
5. Click on Advanced Settings, and then click on Start-up Settings. Click the Restart button.
6. Press the number 4 button on your keyboard to boot to Safe Mode.
7. Login with the built-in Administrator account. 
8. Type cmd at the Windows Search bar and press Enter to open the Command Prompt.
9. Type netplwiz and press Enter to open the User Account settings window.
10. Select your user account, and click on Properties.
11. Navigate to the Group Membership tab.
12. Select the Administrator option and click OK.
13. Restart your computer. 

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