TreeSize

TreeSize is a hard drive tool that scans and analyze all files and folders and show the space used. Is designed to view hard disk space usage in order to make better decisions when you want to delete and make free some space. It features a tree view mode and users can easily view hierarchical structure with details for each folder (size, number of files etc.).
 
Allows to display NTFS compression rate and can scan all folders – even those with no regular access (only view file size, no access to content of those files).