Today FS-Advisor will tell you how to extract wallpapers from windows 7 theme pack. I have found two way to extract the wallpapers from the windows 7 theme pack.
1:  Install the theme pack onto your system. then follow the following steps
goto folder options, tick the check box "show hidden files" then

THEME FOLDER:  Folder of theme

2:  Or You can use another most easiest way to extract the theme ingredients of any theme pack. Jus download and install 7-Zip 4.65  or 7-Zip 9.10 beta 
After installing just right click on the theme pack and click extract and thats it...