Try uninstalling the demo and then installing the game. Normally you shouldn't have to do this but maybe there's a conflict.
I've done so, however the only option that pops up is labeled "demo" 72MiB
Not sure what's happened but you've got the wrong file, the full Windows version is 85MB.
After a month it allows me to install the correct file! GG
Great, glad it works for you now!
