title: Making sure C# program can run on machine with only .Net v2
body: <p>I'm using VS 2005 Standard SP1, with .Net 3.5 SP1 installed on XP.<br>
  The client machines only have .Net 2.0.50727 installed (also on XP).<br>
  How can I tell the compiler to reject any classes or methods that are not available in .Net 2? </p>