Windows Vista Folder Size

I am sure alot of people are already aware of foldersize, an awesome little program to add a foldersize column to windows explorer:-

http://sourceforge.net/projects/foldersize

Biggest problem with foldersize is that it doesn't work with Vista/Windows 7, I have recently got to the stage on my C drive where I have little remaining space but can't find where all the space is being used. Short of going through every folder to find my missing hard drive space I needed to find a solution, I wanted to find something similar to the Disk Usage Analyzer in Ubuntu. There are tons of programs out there but I decided I wanted to use the Disk Usage Analyzer in Ubuntu.
I already have a virtual Ubuntu machine using Sun VirtualBox, so all I had to do was start the share in VirtualBox and then mount it in Ubuntu. Fortunately all this was detailed on the following blog:-

http://www.giannistsakiris.com/index.php/2008/04/09/virtualbox-access-windows-host-shared-folders-from-ubuntu-guest/

Once I had followed the steps in the above post I could open Disk Usage Analyzer in Ubuntu and see a break down of my drives (and found that winsxs was 16GB).

If anybody has any suggestions of a similar tool for Windows Vista or 7, preferably free and not full of spy/ad ware then please post a reply.