If you were jealous of the radial map disk view found in the previously posted, Linux-only toolsFilelight and Baobab, OverDisk brings that same circular goodness to your Windows machine. Point it at any disk or directory and it analyzes the contents and returns a radial map of the folders and files found within. Analysis was surprisingly snappy in a test run, as OverDisk crunched the numbers on 800GB worth of files in under 15 seconds.
Once the results are back, you can mouse over the wedges on the radial map to see which folders and files are chewing up your disk space. If the wedges are too small to select with ease, clicking on any given directory in the radial map will re-render the map with the sub-directories and files for that specific location. The graphics might be primitive by modern standards, but the response time is lightening fast and the interface is easy to use. According to the author's site, he's working out a bug where multiple refreshes can lead to a crash, but during our testing, zooming around multiple disks and terabytes worth of data, there wasn't a glitch to be found. OverDisk is freeware, Windows only.