i believe machine hashes are used to join machines to the domain, so if you crack a machine hash, then i believe you can use it to join a rogue machine to the domain.
edit: but you are very unlikely to crack one hashed as ntlm, i believe the keyspace is 62^14. so you really can only crack them if you have lm hashes.
edit: but you are very unlikely to crack one hashed as ntlm, i believe the keyspace is 62^14. so you really can only crack them if you have lm hashes.