Since the .NET Framework 3.0 includes only new components that are added to the .NET Framework 2.0 and there is no overlap between the assemblies of the .NET Framework 2.0 and the .NET Framework 3.0, there’s no real “Side by Side” scenario. You can run applications based on the .NET Framework 2.0 and applications based on the .NET Framework 3.0 on the same machine.