how to load one swf file into another fla file in flash?

Answer 1

ok .. if what u mean is loading SWF in FLA file .. then simple go to Files > import .. and select the FLA file u want to import > OK ..

else .. if what u ment is to load one SWF in another .. then all u have to do is use the function :
on (release) {
loadMovieNum("theMovieuwanttoLoad.SWF", 1);
}

1 is the level where u want to load your new movie .. 0 is lowest and is used by the main movie u r runing .. so the new movie should be 1 .. not 0
Good Luck
Salam

Answer 2

I'm not sure you can: a fla file is made with all the part of the swf file. And I don't think that Flash MX is able to get back the original fla file (project) from the swf file...