I tried to install the current Free copy and it failed. 
Hi Budd, try to download this installer and install from this setup, however I believe this is a system issue with all .MSI (Windows installer) files on your computer.
http://www.emclient.com/dist/v6.0.21151/setup.msi
Thank you for understanding,
Paul.
Paul, I get the same result. I have not had issues running any msi install other than this one.