ffuasnah,
Click on Start, Search, select "All file and Folders", select the drive in question in the "Look in" box, Click "Advanced Options" and make sure you're searching subfolders, system and hidden files, click "What size it it" and click "Large, more than 1mb", then click search.
This will show you all of the large files on your system. I'm guessing you've either installed some large software application, downloaded some large media or program files.
The other possibility is that you have some type of malware infection that's eating up your hard drive space. To check on this, please go to our malware forum at:
http://www.techsupportforum.com/secu...this-log-help/
and post a message there requesting a scan of your system with a description of your problem.
- John