I ran into a problem with trying to run the latest samples of the WIF. I'm building a cool LiveID example with SharePoint 2010. The examples wouldn't run because ASP.NET 4.0 was not installed.
HTTP Error 500.21 - Internal Server Error
Handler "PageHandlerFactory-Integrated" has a bad module
"ManagedPipelineHandler" in its module list
Similar to the old days, you have to run the aspnet_regiis -i command from the C:\Windows\Microsoft.NET\Framework64\v4.0.30319 directory
Chris