Hi:
http://blogs.msdn.com/vijaysk/archive/2008/03/20/running-asp-net-3-5-on-iis.aspx

>I have been using VS2005 since it was released. I just upgraded to VS2008.
>
>When I go into IIS, view properties for my virtual directory/ASP.Net application, and go into the ASP.Net tab, I expected to see a "3.5" option under the "ASP.Net version" drop down. But all I see is an option for "1.1.4322" and "2.0.50272".
>
>I also installed the .Net framework 3.5 SP1 on my production web server. But I don't see an option for "3.5" in the ASP.Net version in the IIS ASP.Net tab.
>
>Should I see this option under versions when using VS2008?
>
>Thanks,
>
>Jerry