Here is a way to verify the SL is actually installed:
- go to C:\Program Files (x86)\Microsoft F#\Silverlight\Libraries\Client
- make sure there is a folder called 4.0 created
In order to make sure the folder is actually created by the installer, follow steps listed below:
- download the "Microsoft Silverlight 4 Tools for Visual Studio 2010", do not run it
- extract files using WinRAR
- find "FSharpRuntimeSL4.msi" in the extract folder
- run the "FSharpRuntimeSL4.msi"