I have made some progress using a USB flash drive. After pressing F12 it does start booting from the USB. I get as far as the language choice screen, I press "Enter" and I get a grey Mac screen with a big "X", which is telling me to click on "continue" to install Snow Leopard. I click but nothing happens, there is a menu at the top but clicking on anything does not work. I have to hold down the power button to escape. So I am thinking the USB stick is not copying correctly. I have followed the guide, I am using a retail disc of Snow Leopard, and version 8.3.2 of Netbookmaker. Maybe I could borrow someone's USB stick who was successful. I have also tried this using an external hard drive instead of USB stick with the same result.