When you back up media files by using Windows Backup on a computer that is running Windows 7, Windows Backup does not perform an incremental backup. Instead, Windows Backup performs a full backup.
This issue may occur if you have the Windows Media Player Network Sharing Service enabled on the computer. The Windows Media Player Network Sharing Service indexes media files. By doing this, the service changes the metadata of the files for tracking purposes. When you back up your media files, Windows Backup detects that these files were changed and then performs a full backup of the media files.
Note To prevent this issue, do not save multimedia content to the Public folder (%SystemDrive%\Users\Public).
To work around this issue, use one of the following methods.
Method 1: Exclude the media files from being indexed (recommended)
To do this, move all the multimedia content from the Public folder (%SystemDrive%\Users\Public) to a specific user or to any other folder that can be shared.
For more information about how to share files and folders, visit the following Microsoft Web site: