You can use Windows Explorer to determine the size of the first level of directories on a drive, but not to determine the overall size of directories and their subdirectories.
DirUse is a command line tool to display directory size information, including compression information for NTFS volumes. You can use DirUse to determine the actual usage of space for compressed files and directories. Version 1.20 - Free -
http://download.microsoft.com/download/ ... _setup.exe
Example: diruse /s /m /q:1.5 /l /* c:\users