In this short article I will explain you how to make PRISM framework with Silverlight 3. I saw some questions on internet over several forums regarding why the PRISM framework is not working with Silverlight 3. The reason is because the PRISM framework and so as we have to update our PRISM assemblies as well.
Step 1:-
Go to this download link.

Locate the download section and get the file highlighted in above image.
Step 2:-
Extract downloaded exe and locate the folder as below.

Open the CAL folder and locate the solution file show below.

Step 3:-
Build the solution and navigate to the following folder and copy the DLLs as shown in below screen shots.

That’s it. Refer these assemblies into your newly created Silverlight project. Everything should be working nice and easy now. Please post any question/comments you have on this.
Thanks.