Every hard disk is too small if you just wait long enough. TreeSize Free is a free tool that tells you where the precious space has gone to. TreeSize Free can be started from the context menu of a folder or drive and shows you the size of this folder, including its subfolders.
You can expand this folder in Explorer-like style and you will see the size of every subfolder. Scanning is done in a thread, so you can already see results while TreeSize Free is working. The space, which is wasted by the file system, can be displayed and the results can be printed in a report. TreeSize Free is freeware for Windows 2000/XP/Vista.