I have looked both on Wikipedia and Hp-Lexicon, and it does not say where the Mirror of Erised is after Harry Potter and the Philosopher's Stone.
Dumbledore informs Harry that it is to be "moved to a new home" but we later find that it is used as the final protection for the Stone. It is not featured at all later in the books.
Would I have free reign to put the Mirror back at Hogwarts? Perhaps, once again, in an abandoned classroom?