Hi bisenberger,

> The file I downloaded from http://moi3d.com/reinstall.htm is Version
> 3.0 Sep-18-2014. Is version 3.1 just for macs?

Yes, version 3.1 is only for Macs, it has changes to support the new "El Capitan" operating system that just came out.

The version 3.0 that you downloaded is the current version for Windows.

- Michael