When you save you save everything that is on the storyboard - so in this case both segements of video.
To generate two separate files you need to:
- put your original file on storyboard
- play and stop at the desired split point
(the storyboard should now show 2 segments)
- now select file / 'save project' and call it a suitable name (eg videowithsplit).
- now go to storyboard and right click on the second video segement, and select delete.
- now select 'save movie file', and this will save the first segment as a separate .wmv file.
- now select 'open project', and re-open the file you saved earlier (videowithsplit). This will bring back your storyboard with both segments
- this time right click on the first video segment and select delete
- select 'save movie file' again, and this will save the second part of the split as another .wmv file