Can't install Windows 7 Ultimate

I'm using a MacBook Pro running snow leopard (v10.6.8) and when setting up Windows 7 with BootCamp Assistant (3.0.4.) I reach the setup screen, but it says "No device drivers were found make sure installation media contains the right drivers" and there are no options under the "Select driver to be installed" screen. I have followed the "Boot Camp Install Setup for 10.6" but it still hasn't worked. I have tried using my Mac OS X installation disc but it doesn't work, and I can't download the support drivers through BootCamp Assistant, it keeps sayin "The Windows support software is not available" any tips?