I do not know how it is possible for you to be getting the error "Unable to install this application because an application with the same identity is already installed." but also not see Skyline in the list of installed programs at "Control Panel > Programs and Features".
You might find some useful information on this page:
After you have unzipped the unplugged installer, you do not have to run setup.exe if you do not want to. You can instead run Skyline.exe directly out of the folder:
I certainly would have expected that using the Skyline Administrator Installer would have given you a usable Skyline that would appear on the start menu as "Skyline (64 bit)" and would run Skyline out of "C:\Program Files\Skyline\Skyline.exe".