there ist now chance to load the driver befor. I can start the sbs2011 in protected mode, install the driver, but then the konfiguration assistand does not start again.
I found a solution.
WHile the assistand check the network, you can user Shift + F10 to start a DOS-promt. Then enter control and the Controlpanel starts. Add the Nic driver from the CD and go back to the Asisstand.