I tried to do a System Restore (I probably should've mentioned that in my first post, but I forgot) but it didn't change anything.
I reinstalled IE6 and ran CCleaner. After this, the automatic update still wouldn't work. However, after doing this, I could go to the Microsoft website, download the exact same update from there, and it worked fine for some reason. I'm not sure if something is wrong with my auto updates, or if it was just that update in particular. I guess I won't find out until the next updates get released.
I was tempted to try installing IE7 again, but I decided just not to bother. Firefox is my main browser anyway, but I just liked having IE7 because it's better than IE6 for when I come across sites that require IE. I'm thinking that the problem may have stemmed from files being removed that shouldn't have been when the IE7 RC was uninstalled. I remember Trotter posting about IE7 doing something like that to him when he tried to uninstall it and go back to IE6, only on a much worse scale since he had to reformat.
Anyway, thanks for the help guys, I appreciate it!
There are 10 kinds of people in the world, those who understand binary and those who don\'t.