Screenblast Movie Studio 3 does not support DivX, so you'll need to get another codec to change the SB MS 3 file to DivX.
I don't know one off hand, but I'm sure someone in this forum knows some.
Assuming you have the codec properly installed:
- Make Movie
- Save it to your hard drive, Next
- Advanced Render...
- Save as type: Video for Windows (*.avi)
- Template: Default Template (uncompressed)
- Custom
- Video (tab at bottom of window)
- Video format: DivX Codec
- OK
- Enter filename
- Save