TREEPIE
Image from treepie.sf.net a simple software to understand what fill your HD. [[ now 1.3 work also on vista ]]
It's a "SUNBURST DIAGRAM" quite difficult to understand at start but the really usefull.
2 link from
Stephen Few about SB diagram:
www.gvu.gatech.edu/ii/sunburst/
www.iro.umontreal.ca/~sahraouh/qaoose2005/paper3.pdf
Flickrmania: make a screenshot of your hard disk drawn by TreePie, put it on flickr and tag it HDtreepie ... or if you prefere directly treepie (but i'ts also a bird :D ).
and.. You can see how treepie work on youtube