I am having this same issue. I can download the installer from the website, but when I try to install it on the computer, it goes until it says "installing files 8 of 58" and then an error pops up saying a problem occurred during installation. It tells me to try restarting the computer and restarting the installation, both of which I have done, but I keep getting the same error at the same spot. 

If I click on more details, it says:
Patch failed to apply with error code: 18

Failure opening new file C:\ProWin20\32bit\ProPrd20.ini

Please help!