Flash CS4 .fla to Flash MX 2004 Professional .fla?

Hello all, I am a new member here on these forums.
I need help on how to convert a .fla made on Adobe Flash CS4 to a .fla file made on Macromedia Flash MX 2004. I have Adobe Flash CS3, if that helps. And yes, I know that it does not matter which version I have to save as a .swf, and it opens with all flash versions, but I need a .fla file I need to hand in to my school's I:// Drive for a project. (My school only has Flash MX 2004, yes I know, bad for an IBT middle school.)

Thank you for your time.

-mehad.