If i reinstall iTunes will I lose all my music and movies?
Generally speaking, you won't lost your music and movies. However, the improper handling also may due to data loss. So, for safety's sake, you can follow the guide below to backup your music and movie to computer first.http://www.any-data-recovery.com/product/itunes-data-recovery.htm
not if you bought it off of the iTunes store it should stay on you're account
No. Just make sure that it's in your iTunes library. If you're switching computers, then yes, you will lose your music, movies, apps, etc.