Ah, that makes sense. I hadn't considered the compression/decompression thing. I looked around for a while to see what folders were free to move (good thought, though, about moving program folders and putting them back before using the program again), and I found my old Dropbox folders there that I didn't need anymore. I deleted those, and I'm all good to go! I'm going to plan on keeping a movable file on all my hard drives for this issue in future, so there's always something I can drag out and free up space for uninstalling.
I'm trying to uninstall Adaware because it's not working properly in several ways, but I can't uninstall it because "There is not enough space on your hard drive." Does Adaware require space on the hard drive to write temporary files for uninstalling? It seems dumb that it should require new space to free up old space, but I understand technology works in strange ways sometimes. My HDD space is indeed very small, and I need to clean it up and move programs over to my secondary drive, so I'm hoping this isn't a common issue for uninstalling or I might be in big trouble.