Your download links not working anymore version after version 4 is out please change with this ones
http://installers.cdn.hitfilm.com/hitfilm-4-express/HitFilm4Express_x64_4.0.5609.10802.msi for windows
http://installers.cdn.hitfilm.com/hitfilm-4-express/HitFilm4Express_4.0.0113.pkg for mac
And those are also version 4 not for versiyon 3 but working well still!!