Windows 7 - Installing .NET 3.5 SP1 on Win7 RC

The RC of Win 7 apparently comes with .NET 3.5 already installed. Does it include .NET 3.5 SP1? The Windows\Microsoft.NET\Framework\ directory has a 3.5 directory, but not a 3.5 SP1 directory which I usually see on XP machines that I have updated with SP1.

When I try to install the 3.5 SP1 download, it tells me I have to use "Turn Windows Features on and off" from the control panel to install and configure .NET 3.5 SP1. But it doesn't explain how to do that. Checking and/or unchecking the .NET 3.5.1 checkbox doesn't seem to do anything except put up a slow moving progress bar. If I then respond to the "Your program didn't install correctly" box by telling it to install with recommended settings, it goes ahead, asks me to accept the T&C, then downloads 0MB, and promptly gives me a setup error.

I've tried this on two different installations, one on an AMD Athlon 3500+ box, and one on a Virtual PC running on a Dell Dimension laptop. Same results on both of them.

Thanks for any advice.