If you are wondering what files is consuming your drive space on your PC, you may want to download and install TreeSize Free. gHacks has a good review on the newest version (see source link below).
TreeSize Free analyzes disk space usage of a structure, e.g. a drive or folder, and displays information about the number of files, total size of files on the storage device, and more, in its interface.
Source: TreeSize Free 4.3: usability improvements and PDF exports – gHacks Tech News
