Flash CS3 slow running

Hi,this is a stupid thing, but have just moved to a new iMac and running CS3. Even though I am creating movies with publish settings set at action script 2 and version 8, when I test them on a slower processor they just won’t run, they are painfully slow and all the sync and music is thrown out! Very frustrated, very tearful and don’t know what to do. Has anyone had this problem and can they offer a clue?:sad: :crying: