How to get rid of Windows.old folder after the upgrade to Windows Server 2012?

After the server is upgraded to Windows Server 2012 there is an useless folder in the root of C:\, titled Windows.old. This folder is BIG: ranges from 10 GB to 25 GB in size, depending on the role of the upgraded server.

So it’s better to remove that folder, but how? In Windows Server 2008 R2 you had the Disk Cleanup button located in the Properties screen of every logical disk shown in the Explorer. But in Windows Server 2012 this button isn’t present any more by default:

The folder Windows.old is locked by default so it takes some time to gain permissions on ALL those folders found in the main folder Windows.old. So that’s not the way to go.

Gladly in Windows Server 2012 there is a better way: Just get the earlier mentioned button back. How?
1. Start PowerShell on the related Windows Server 2012 machine;
2. Enter: Install-WindowsFeature Desktop-Experience and hit <ENTER>;
3. It will run for some minutes and report when ready;
4. Reboot the server, the feature will be installed and initialized while rebooting. This takes some minutes as well;
5. After the server is fully functional again the button Disk Cleanup is back again:

6. Hit the button and after the scan it will show you next window;

7. Hit next button - "Clean up system files";

8. Hit the button and after the scan it will show you the option to remove the Windows.old folder;

9. OK > Delete Files;

10. It will run for some minutes;

11.After a while the Windows.old folder is deleted.
When required, the PS-cmdlet Remove-WindowsFeature Desktop-Experience will remove this feature again from your server.