Well this seems simple at first, but it is actually pretty comlicated. McGonagall transfigures things to be alive, like the suits of armor in the seventh book and the chesspieces in the first book. At first this seems more like a charm, because they don't seem to actually change in identity; they are still just suits of armor and chesspieces. I can see this as transfiguration, because she is changing the objects to have life imbued in them instead of being inanimate objects. Their identity changes by them now being alive. They go from being nonliving to living.
Charms are more of just using magic to move things, rather than change them. This is just one example of how Transfiguration and Charms can sometimes be hard to distinguish.
I have no answer for this occasional riddle, but I have to say that it is one of the things that makes me simply in awe of the series when I think about it. JKR wrote some very complex books; so complex, that even simple deviations in subjects is difficult to understand. But here is my quick advice on the subject: Transfiguration changes the nature of the object itself, and Charms only causes the object to do things but never to change identity.
Mischief Managed.
Calie
