Microsoft Silverlight is a native program in Windows that allows you to watch videos in your web browser. Netflix is an example of a company that makes use of Silverlight to stream videos to you through your browser. An effective way of saving a Silverlight screen on your computer as a video file is to use a screen video capture program. These programs can record what plays on your screen and save it to your hard drive.
Download and install BSR Screen Recorder (see Resources). The program captures all video and audio occurring on your computer and outputs it into a format like WMV. BSR is free to use but adds a watermark to the file until you purchase the full version.
Use Debut Video (see Resources). Debut Video records your screen as you play streaming video through Silverlight and saves it to WMV or AVI. The program is free to use for a 14-day trial.
Try Easy Screen Capture Video (see Resources). This program is completely free to use, though it has a nag screen before you buy the full version. It will save your streaming Silverlight video to AVI, though it doesn't record sound.