It is a good practice to sweep all garbage from your computer at shutdown. Here is how you can setup CCleaner to sweep your Windows 7 at shutdown automatically (assuming that you have installed CCleaner).
Right-click anywhere on your desktop and choose New – Shortcut. In the location field, type the following command and click next.
"%programfiles%\CCleaner\CCleaner.exe" /auto /shutdownRename the shortcut something like Run CCleaner or anything you like and click Finish.
This would create a shortcut for CCleaner on your desktop, double-clicking on it would run CCleaner in the automatic mode and then shutdown the Windows.