I signed a non-compete for an office supply company 4 years ago, does it still apply?

There is no time limit on contracts--the fact you signed a contract four years ago does not make it invalid today. Also, changing your position or your location (e.g. being transferred to a new state) within the same company would not invalidate or terminate the non-competition agreement, unless the agreement specifically said that it only applied to the job/location you had when signing; otherwise, there is no need to sign a new non-compete and the old one would remain in force. From what you write, you would seem to be bound by the agreement.