Loading .swf movies into a movie

I did the tutorial on kirupa: http://www.kirupa.com/developer/mx/full_site.htm

I have an animation with my basic layout of my site = 39kb
There are 2 buttons. I have put the code as explained in the tut on both buttons. The 1 .swf (668kb) loads into my contents movie and the other .swf (283kb) loads into my contents movie when clicked on the second button.

Problem:
As soon as I put a preloader into 1.swf and 2.swf loading into contents movieclip the 2 buttons doesn’t work. So now there are no preloaders anywhere and everything works fine on my computer, but it takes a couple of seconds to load on a friends computer. Surely the movies being loaded must have preloaders or not?

i hope this makes sense?