Strictly Scott is correct, but unfortunately the ".NET" name is overloaded. ".NET 3.0" does not include any updates to the Common Language Runtime (the core execution engine), the Base Class Library, Windows Forms, ADO.NET or ASP.NET, which remain unchanged from their .NET 2.0 versions. The only parts that are new are Windows Presentation Foundation (WPF), Windows Communication Foundation (WCF), InfoCard and Windows Workflow Foundation (abbreviated WF). .NET Framework 3.5 will also be 'pure extensions' to .NET 2.0 but will require .NET Framework 2.0 SP1 to be installed, which will ship at the same time. I'm not completely sure how this will work out, whether System.dll will be replaced or not. So the answer is, if you're targetting Windows Forms or ASP.NET, you need .NET Framework 2.0, but if you're using WPF, WCF, InfoCard or Workflow, you need 3.0 as well.
DoEvents: Generating unexpected recursion since 1991