First, DO NOT use a hammer and nail. We call people who do that hammer mechanics. Yes, this is a derogatory term. Second, soak the cup with some sort of penetrating oil and let it soak over night. Go the LBS and get a pin spanner. Now you should be able to remove the cup. IF YOU MUST USE A HAMMER GET PUNCH OF THE PROPER SIZE AND TAP, NOT HIT HARD THE CUP.