Fixed background when scrolling

I’m trying to make a background for a html page remain static so content will scroll on top of it. Here’s the catch. Imagine a horribly designed myspace page with miles of content you have to scroll through from top to bottom. I’d like to be able to have a swf as a background at a set size (i.e. 800x800) an every time a user scrolls down the page, the swf relocates itself to the top of the browser window. I already have the swf in a div behind the content (div), only problem is that it is static at the top of the page. Once a user starts scrolling down you can’t see it anymore obviously.

So does anyone have some sample script or links to tuts to achieve this?
I know it’s possible through use of DHTML or just some javascript alone, I just can’t figure out a solution for my exact problem.