How to clean up old application folders from prior ROM?

I installed CM10 on my GS2, and during the process I didn't format the file system as I wanted to retain my photos and music on the device. I was aware of an app called "SD Maid" that is *supposed* to be able to be able to clean up all these old app folders, but it doesn't seem to work. Does anyone know how I can clean up all these folders, or does a person have to just go in and manually delete all of them? (For an app to do this, the OS would have to have some sort of a referencing system of known installed files & folders, don't know if it has such a thing though.)