Ok can some one please help me with this. My sister and I were talking about this movie that we both loved as kids. Its about a boy and girl that for some reason want to have a Halloween party in this old mansion. The problem is that the house is in habited by this old witch and her cat. The old witch is really thin has a huge nose and has a black cape. The only thing that is different in this from other witches or at least what I can remember is that she doesn't have a traditional witch hat but has what kind of looks like a ski mask that allows you to see her entire face. I know its really obscure facts but this most of what I can remember. I do have a vague recollection of the song at the beginning. Mind you I was five at the time when I last saw this, but I swear they lyrics would say some like "western magic halloween?" I could easily be wrong but that's what I remember. Hopefully you guys can help

Well, you didn't say if this was live action or an animated movie. If it is animated, then I think I know what it is. Its called Witch's Night Out.
Here is a description from Wikipedia:
The plot involves a witch who accompanies two children named Small and Tender with their babysitter (Bazooey) to a Halloween party and transforms them into a werewolf, Frankenstein's monster, and a ghost (previously their Halloween costumes). The witch takes them to the Halloween party-in-progress at her house. Other citizens of the town get offended. They try to catch these supernatural beings as a mob. The children and Bazooey spend the night as real eerie creatures but decide they need to become human beings again. A disco song entitled "Witch Magic" was sung in this film.

This might be what you saw. Hope I'm right.

Thank you so much!! Lucas2009 that's the movie! Can't wait to buy it so that my sis and I can show our kids our favorite Halloween movie.