The steps are spelled out on the screen when you are running the wizard. So you are getting to the point of browsing for the file but you can't see it in the browse window of the Wizard?

Maybe try putting the .bin file on your Desktop or some other directory, just in case the My Downloads directory isn't accessible for some reason (but that would be strange). And you could rename it to something short, like "OS2008beta.bin" in case it has picked up a character that the wizard doesn't like (though the default name seemed fine when I did it).