by Don Burnett

If you are having problems with Silverlight after SP1 installs of either Visual Studio 2008 SP1 or .Net Framework 3.5 SP1, then it's probably more than likely that you haven't cleanly uninstalled ALL OF the previous beta bits properly...

Try this:

1. Uninstall all Silverlight 2 elements from Programs
2. Download and run the patch removal tool here (Please make sure that you uninstall all patches to VS2008 that you find in Programs and Features before running  this tool)
1.  http://www.microsoft.com/downloads/details.aspx?FamilyId=A494B0E0-EB07-4FF1-A21C-A4663E456D9D&displaylang=en
3. Check again to make sure that all Visual Studio 2008 patches are removed from Windows Update/View Installed Updates
4. Download and run VS2008 SP1 installer (includes .NET 3.5 SP1)
1. http://www.microsoft.com/downloads/details.aspx?FamilyID=fbee1648-7106-44a7-9649-6d9f6d58056e&DisplayLang=en
5. Download and run the updated chaining installer for Silverlight 2 Beta 2
1.  http://www.microsoft.com/downloads/details.aspx?FamilyId=50A9EC01-267B-4521-B7D7-C0DBA8866434&displaylang=en

After this Silverlight 2 Beta 2 should cleanly install and be cooperative with the new WPF install as well..