Unfortunately, the answer is that you can’t change the background in Windows 7 Starter Edition. This particular edition of Windows 7 was developed specifically to run on lower-powered systems such as netbooks and as a result, includes a limited feature set. In other words, it does not include the all the features and capabilities you would expect to find in Windows. As a result, the ability to change the background was removed in Windows 7 Starter Edition to eliminate any performance issues on lower-powered systems.
To find out more about Windows 7 Starter Edition, click here.