I would not disconnect the battery, people have replaced a battery before and caused the IBS to fail. That is $200 or $300 I believe and BMW could refuse to warranty it.

Try putting the remote in the slot located in the glove box and start the vehicle unless your E70 has it where it is on the steering column. Anyway, there is a place where you hold or put the remote for when the battery in it is dead. Try using the remote that way for the first time and see if that gets it programmed.