Windows Support XP/Vista/7

Question

I have writen some C# software, which basicly writes and reads from a database to gives communication betwean PHP website and C# application.

I'm useing Visual Studio 2010 Pro but can only drop support back to .Net 2.0
I would like full support for my software from Windows XP Original which i belive was .Net 1.1

Does anyone have a Good solution for me?, ive heard that mono takes out .net support alltogether is this correct?
if not a better solution.

Thanks in advance!