I'm sure 97% of this is not possible in Silverlight. Silverlight is isolated for security, so you do not have full access to the client machine. This means that creating a WMV animation record would be impossible.
Even if you used WPF, which would have direct access to the client machine, it would be difficult or impossible.
Why don't you give more detailed information about what you are trying to accomplish, and perhaps we can give a better answer.