Both .mmsw and .scw files are used by Movie Magic Screenwriter for its documents, however the first is from OS X version and the other from Windows. It appears you should be able to re-save one to another using the program, at least in some of the versions.
Convert Movie Magic Screenwriter document to Movie Magic Screenwriter document.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert mmsw to scw on Windows
Movie Magic Screenwriter is professional tool used to write screenplays. Movie Magic Screenwriter is able to format screenplays, automatically put character names, scene headings, and actions in the appropriate places.
Convert from mmsw file
to scw file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.