The Silverlight player will play WMV files, and it requires WMV streaming information in the file.
Digital Media Converter Pro will convert your files to a streaming WMV file format.
To reduce the size of the file - click on Select Format, then select WMV for Internet Streaming and click Configure. Choose the Screen Capture setting and convert. You should have a file that is much smaller and provides good viewing quality.
Download a free evaluation of Digital Media Converter Pro here.