Hi Kendra, have you run WinDirStat to get a good visual view of what's taking up the most space?
Also, have you run CleanUp! to make sure all the useless clutter has gone?
No, you're mixing Bridge up with Lightroom. Bridge can be anywhere, and nothing gets messed up.
However, I wouldn't recommend moving Bridge (please understand that I am no Brian, I'm just filling in time until he gets here). Instead, I recommend making a new folder on your D drive called "Bridge Cache Don't Delete" or whatever; then in Bridge, go to Edit>Preferences and to the Cache tab. In there, you'll see where you can choose to have your cache folder. Choose the new folder on your D drive. By default, its cache is probably on C, and that hurts a bit. Also, while you're in that window, hit "Compact Cache".