Marisa419, I recently renewed my empadronamiento without any problem (which was necessary to have before my NIE renewal appointment in March 2011). My renewal form says at the bottom, "En caso de altas, bajas, y/o cambios de domicilio, diríjase a cualquiera de las Juntas Municipales de Distrito, al teléfono 010, o a Internet www.munimadrid.es . I don't know for "altas" (new registration for your living in a particular district) - as is your case. I didn't have to make an appointment for my renewal, I just showed up and waited for about an hour with my take-a-number in-hand, and they made the changes/approval in-the-moment, but I had the form already filled out. And, yes, you'll need the empadronamiento form for your NIE appointment, photos, copies of every page of your passport, and whatever else they say you need.

Let us know how it goes! Saludos, MadridMan