How to install SQL Server 2008 on Windows Server 2008 R2 RC

I was trying to install SQL Server 2008 on Windows Server 2008 R2 RC.

But, when I launch SETUP.EXE, Windows warns me that SQL Server is not compatible with Windows Server.
If I ignore the warning, the install proceeds but then fails to install .NET 3.5.

After a little searching and experimentation I found a way to install without any problems:
1. Create a slipstreamed SQL Server 2008 SP1 install, follow the instructions here.
I set my my PCUSOURCE=”.\PCU” and that worked fine.
2. Add .NET 3.5 by going to server manager and adding the .NET 3.5.1 feature.
3. Install by running SETUP.EXE.

I hope this helps somebody.