C++ app (Win32 emphasized, yet x-platform) downloader. cmake

I need source code that can be compiled into a single dependency-free .exe file. First the app checks to see if something is installed (if it is already installed, it displays a MessageBox 'already installed'). The app goes to a web page and downloads a few .exe files to a cache folder (c:/cache) unless they already exist. It then runs the .exe files, passing in some switches as it's parameters. Only one instance of this .exe can run at a time, plus don't display anything in the task bar or any console windows (silent install). I'd like you to use CMAKE as the build system and cygwin as the environment from which the compiler is installed. This requirement is just so that your compilation sequence is repeatable by me and others. If you think you have another compilation vector, feel free to share it and I'll research its practicability. As a flair, I'd also like this app to compile on linux and mac, and download the files to a cache folder, BUT instead of trying to run them (they'll be win32 binaries) simply COUT "win32 binaries cached, but can't be installed due to platform incompatibilities". This requirement is only so I can see a decent x-platform C++ template for future tweaking.