Paste each of the following lines into the address bar of a windows explorer window, and hit enter. (see pic to the left for clarification) Once you are inside the folder, double click the XX.theme file in there to install it. If you browse the folders manually instead of using these links, you will need to disable hidden files and folders.
%windir%\Globalization\MCT\MCT-AU\Theme %windir%\Globalization\MCT\MCT-CA\Theme %windir%\Globalization\MCT\MCT-GB\Theme %windir%\Globalization\MCT\MCT-US\Theme %windir%\Globalization\MCT\MCT-ZA\Theme
I’ve also seen that some of the following country themes exist, though I don’t have access to them on a US licensed version of Home Premium. If you want to see everything you have available, just browse back to the MCT folder, and see what’s in there!
Each time you double click a theme file it will open your personalization control panel, so you may as well leave it open until you’re done. Once all your themes are installed, enjoy all of your new choices!