There are a total of 5 additional hidden themes which are categorized by Region. These are Australia, Canada, Great Britain, United States and South Africa. You can enable them by doing the following:
•Go to folder options, there are 2 ways to do this, (Press Alt inside Windows Explorer you will see the hidden Tools > Folder options OR Click Organize > Folder and search options) Either way it will lead you to the same dialog
•You will find 5 folders which are the 5 different hidden Region themes. Lets go to Canada for example.
•Click the theme CA icon, this will enable your theme to Shift to Canada
So by doing this you can view and add more themes to your Windows 7 without downloading or making any addition changes. Lastly remember to turn off the show hidden files for security reasons.