If WinDirStat is not installed on your computer and you have an account that is part of the administrators group; this application can be downloaded for free from the SourceForge project page. (Click on the images below for a larger view.)
Go to the start menu and click"All Programs" then click the "WinDirStat" with a folder icon and finally click "WinDirStat" with a tree icon.
If you do not wish to generate statistics on all the drives, select the one or ones for wish you would like statistics generated.
Click the "OK" button and wait for the Pacmen to go away.