5 megs in size but 30 seconds long..
No. You mostlikely stuck a full MP3 in your flash which increases the size dramaticly. I suggest getting a freeware MP3 to wave converter. Converting it to .wav, then editting the quality in Microsoft soundrecorder. (yes you can do this)
Once said MP3 has been converted open it in Sound recorder and:
File > proporties > convert now > and choose something of less Hz/Kb, but doesn't make it sound overly crappy... Also, if your movie is extremely short while the song would go on for 3 minutes, choose the position your movie ends and Edit > Delete after current position.
Your movie could most-likely be downsized 4 megs or more.