.NET support not found on this computer.

I am trying to load Grasshopper into Rhino 4 on the windows side of my Mac. While loading I am getting error messages: I have .NET 3.5 installed on my windows, but In the Windows control panel the Grasshopper download does not register any file size
Rhino Plug-in Error
GrasshopperPlugin.rhp
GrasshopperPlugin.rhp load error. Plug-in identified as .NET plug-in but .NET support not found on this computer.
