Hard Drive Visualizer
If you said yes to any of those questions, WinDirStat might be just the program you've been looking for! WinDirStat can show you a list of all of the files on any particular drive, and then gives you a color coded representation of all of them, so that you can see which types of files, and which particular files are taking up space on your hard drive. Now you can figure ouw which of those audio, video, or other data files is clogging up your drive, and remove them.
The great part is, it's free! It's open source, but it is currently only for PC. We thought it was just so great, that we had to share it.