Download and install a free video converter program such as AVC Video Converter (see Resources). AVC allows you to decrease video size to the resolution you want as well as change it to a different video format it you choose to.
Launch the application once the installation is complete and click "Add Video." Locate your WMV video file from your computer and click "Open" to import it to your program.
Select "Customized WMV Movie (.*wmv)" on the profile window. Scroll down to the "Video Options" section.
Select a smaller video resolution to reduce the file size. If your input WMV file had a resolution 1280x720 resolutions, select a smaller resolution such as 720x480, 640x480 or even 320x240 if you want a very small video. Reducing the resolution significantly reduces the file size.
Select a lower bitrate setting. For example, if your input WMV file had an 8,000 bitrate setting, drop it to 5,000. Higher bitrate settings yield higher quality outputs but with larger file sizes.
Select the audio codec to use and the audio quality settings. Select the audio channels (stereo or mono).
Click "Convert/Encode" to begin the conversion process. A status bar shows the progress of the conversion.
Locate the WMV video file once the conversion process is complete and right-click it. Click "Properties" to see the file size. The WMV file is smaller than the original video depending on the settings you chose.