I've run into this issue as well with the current demo build on Windows 10 (64).
1. When initially installing the demo, I used the Game folder that other games on this system were installed in. When doing so, I got the same installation "System.FormatException" reported in this thread: viewtopic.php?f=8&t=59
2. I hit "Continue", but was unable to do anything else and the installer didn't appear to be doing anything.
3. I closed the installer and ran the Launcher, which appeared to run but also didn't do anything for several minutes.
4. I uninstalled the game using the uninstaller in the game folder, and received an error. All files were removed from the game folder with the exception of the uninstaller itself.
5. I manually deleted the uninstaller as well as the containing folder.
6. I attempted to install the game again.
---> I received the message saying the game was installed.
In an attempt to resolve this, I tried the following:
1. Check "Programs and Features" - the game was not listed.
2. Manually check the registry using regedit in areas I would expect the game to have recoreded info.
3. Ran searches in the registry for "cure" and "cryogenic" - no results.
4. Ran file/folder searches on all of C: for "cure" and "cryogenic" - found a few log files and deleted them.
5. Ran CCleaner to remove temp files and such.
After all of these, the installer continues to say that I have the game installed.
While it would be great to have the installer provide options to fix/uninstall as well as doing a fresh installation, knowing where the installer is looking to verify that the game is already installed would at least allow users to resolve the issue themselves until it can be fixed.
I'm super excited for the game, so I hope to be able to try it out soon!