Update 11/20/09: The Surface SDK is now available to everyone at the new Surface website! The instructions below should continue to work just fine…let me know if they don’t.
Update 10/29/09: It appears that the version of the SDK available from the Microsoft Partner site comes as a straight .exe file. To extract this back into the MSI file to follow the instructions below, execute the following command:
"Microsoft Surface SDK 1.0 SP1, Workstation Edition.exe" /extract c:\surface
This should spit out a MSI file to the c:\surface directory and you can continue on with the instructions below. Thanks to Tim Hurst for the info!
The Surface SDK SP1 Workstation Edition