2. Click this button in it
and then the "patch files" button.
3. Now click this button
and click "patch files".
4. Reboot.
5. Download new themes from here or somewhere else.
6. Put the downloaded files into the "C:\Windows\Resources\Themes" folder.
7. Finally goto Desktop -> right click and select "personalize". Select "Themes" and select your new theme and apply. Done.