After doing what the wiki instructed, I now have even more problems.
Basically, I did the "Rename, Move, & Copy Files, using "Update database to point to new location (no file rename, move, or copy) for all the files in my music collection. I would find "A:\Mp3" and Replace with "B:\Mp3," and it seemed to work, but I had forgotten to remove A: from the library folder monitoring and add B:. So I ended up keep on getting A: files added back to the MC database, and I thought something was wrong, so I did the find/replace a few more times until I finally realized what the problem was. By then, I already have many duplicates, and they cannot be rid of by using "remove duplicate." The duplicates all point to the same file/location, and I have no idea what to do other than manually deleting them one by one, and that's just not possible since I have a gigantic music collection.
So what do I do now?