.NET 3.5 SP1 missing when installing Commerce Server 2009 on Win 2008 R2

When you try to install Commerce Server 2009 (after the 2007 install) on a Windows Server 2008 R2 you will get an error saying to install .NET 3.5 SP1.

You may try to install it, but you cant, when you try to install it extracts and the installer vanishes...you know why? R2 already comes with 3.5 SP1 (a warning on the installer saying its already installed would give us a better clue)

After some poking around we found a MS hot fix...a reg key is missing on the 3.5 SP1 of the R2.

Request the fix to support: http://support.microsoft.com/?scid=kb;en-us;975567&x=14&y=13

Please stay around for more CS2009 info and also check my colleague Marco's Silva blog, for it will have soon more CS2009 goddies ;)