Diesel.com Flash Help

Hi I’m new here and just wanted to say what a great site/forum.

On the www.diesel.com website they have 2 swf files that display the content. Now 1 is the main content swf, with menus etc. That’s not my problem. What I was wondering is how they made the background picture a swf file that re-sizes itself with whatever the browser window size is.

I hope somebody can help me out. Thanks very much.