Problem: Let A be an nXn matrix with complex entries. Prove that AA*=I if and only if the rows of A form an orthonormal basis for

Thoughts: If AA*=I then A*=A^-1, but I don't understand how (or if) that implies that the rows of A are an orthonormal basis, or how the reverse is true, or, for that matter, much of anything involving linear algebra, gah!

Thanks for any help.