How do you forget HM moves in hearth gold?

In Pokémon HeartGold, you can forget HM moves by visiting the Move Deleter, who is located in Blackthorn City. He can remove any move, including HMs, from your Pokémon's moveset. You'll need to have your Pokémon with you, and the service is free of charge. Simply speak to the Move Deleter, and select the Pokémon and the HM move you wish to delete.