Have you installed Service Pack 1 for Vistual studio 2008?
fretje
2009-07-05 00:14:23
The installer for .NET Framework 3.5 SP1 is not included in the VS2008 SP1 installer due to size restrictions.
For a workaround on how to actually include it in your setup project, refer to this page: http://blogs.msdn.com/vsto/archive/2008/11/18/how-to-include-net-framework-3-5-sp1-with-your-installer.aspx
Just to add my two cents. After installing SP1 for Studio 2008 I still don't have .NET Framework 3.5 Client Profile available as prerequisite.
But If I select .net client profile and .net framework 3.5 sp1 then .NET Framework 3.5 Client Profile gets installed.
I suspect this is a glitch in studio 2008, but apparently it works.