Update Boot Camp 3.0.1 to 3.1

Hi guys!

I've Snow Leopard with BootCamp 3.0.1 and I would like to install windows 7. So then I need BootCamp version 3.1. How can I update BootCamp? I just have found to download an .EXE file for update Boot Camp....It can be updated without having installed a Windows OS?

Thanks!