Xinorbis is a interesting hard disk analyzer that compiles heaps of information about files on the hard drive and presents the results in easy to understand manner using text and charts. The analysis takes a while to complete because all files are scanned on the hard drive that you select.
The analysis does not only count directory sizes but uses the information to put the files into categories like system, office, graphics and movies. Each category displays its file count, total file size and the percentages of both. Additional statistics provide information about the percentage of file sizes on the hard drive, file dates, top 50 largest and smallest files, files with 0 Kilobyte and file extensions.
Reports can be generated and exported as html or xml files. Xinorbis can also do a full drive / partial drive comparison which is interesting if you are mirroring partitions or want to compare differences between hard drives.

The downside of this program is that it is not responsive during the scan of the hard drive. It takes a few minutes to scan a normal sized hard drive but the comparison took more than an hour before I stopped the program from running.
Related posts:
- Windows Directory Analyzer
- Disk Space Analyzer
- Log Analyzer To Search Multiple Log Files Simultaneously
- Replace Scan Disk with Check Disk
- Microsoft Visual Round Trip Analyzer
- Apache Web Log Analyzer
- Audio Analyzer For Lossless Audio Formats
- Portable Free Stopwatch Program

I think windirstat is a superior app.
http://www.ghacks.net/2005/12/page/3/
Looks like Xinorbis gives you far more information than WinDirStat plus it doesn’t have that hideous visual view.