Hardly should not be used as the adverbial form of hard; hard itself performs this function (hit someone hard; be hard pressed). Hardly means the same as barely or scarcely and, like them, has an in-built negative effect, so that I can hardly see and hardly anything are correct, and I can't hardly see and nothing hardly are incorrect. When hardly begins a sentence, the usual order of auxiliary verb and subject is reversed: Hardly had the meeting begun, when trouble erupted. Note that the clause following this construction should begin with when or before, not than