Creating a split screen video of a multitrack recording
WAX is an freeware video editing program. 

You can create a split screen effect with either a source image or AVI video file. Import then source files into the MediaPool (Project -> Insert Tracks) then position them on seperete layers on the timeline.

From the MediaPool change to the Plugin Presets tab and drag the desired split screen effects over the video/image you wish to apply.

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I've shown an example above, in the second screenshot you can see I played with some of the settings to adjust the width of the split screen. You can also change the size and position of the video.