I use a nice tool that helps me figure out which folders holds the most disk space on my computer. The tool called TreeSize Free and it highly recommended.
Every hard disk is too small if you just wait long enough. TreeSize Free tells you where 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.