Using preloaders throughout an all flash site

I am working on a project that will be too large to load the entire movie at the beginning. I would like to add preloaders to portions of the site when a button is clicked, it calls up that segment. I’m not sure if this is done with external movie clips or external swf’s. I also have noticed that my preloaders at the beginning of a site only show up at around 25% or not at all, especially with IE7. Can someone shed some light ?

:q: