Here is some ways
I've run across alot of horribley large intros in the past, and one of the best ways is to reduce all jpegs in the document down to half their size and then scale them in flash... it kinda lowers the quality but unless you really look its not that noticeable...
another way around the giant picture problem.. is use adobe photoshop/image ready and select file - > save for web.. that can create incredibly small files..
another reason could be your background music.. if that is large there is no real way to shrink it unless you have acid pro 3.0 or adobe audtition.. they can both compress files and such.. also always try to use mp3 files, they r smaller than wavs...
the final reason that isn't very likely is that you could have inserted a video clip.. lol.. which I have done in the past for commericals if thats the case, I'd find a way to get ride of the clip all together.. because movie clips are usually just big files..
finally if all else fails... when your exporting the movie, just turn the jpeg quality down to 50 or 75 that usually lowers the size by a bit..
hope that helps if not ohh well.. I tried..