Attached Link: http://www.jam-software.com/freeware/index.shtml

I've been using the freeware version of Treesize. It provides a Windows Explorer tree with the sizes of each directory (ordered largest to smallest) rolled up to the highest level. Clicking on the "+" shows how much space each subdirectory uses. I haven't tried SpaceMonger, but it's graphical representation looks less straightforward than Treesize. I've provided a link in case somebody wants to try it.