[puma]

You should be fine with compiling in .NET Framework 3.5 though, no need to go any lower than that, because most computers should have it by now. If they don't you make then download it, and if you want to use .NET Framework 4, personally I say go for it, just get the end user to install it, it's for their own benefit too.

That's the point of the installer. It's downloads it for them and installs it silently in the background. Obviously, if your installing something they want to install then they'll install it for themselves.