You've got many useful answers but I would like to say my opinion. As far as you've installed the latest version of Bootcamp Assistant for Snow Leopard I would only runit let it automatically download the drivers for Windows.
Then, install Win 7 and the driver's you've previously dowloaded. If there are updates to those drivers you can do it through Bootcamp app into Windows.
Regarding the install of Win, in my large experience in the matter, many CD/DVD of Win can give problem of not starting install or performing a bad install. For many I had to change the install CD/DVD, for some, washing them with soap and water and cleaning with a soft sheet is a wonderful thing as many don't know the worst thing we "do" to CD/DVD is holding the written surface with hands which, you know, have e thin film of fat on it and is a very deletery thing for reading/writing CD/DVDs.
HTH
Simon