You can install both frameworks at the same time. They install side-by-side by default (no upgrades)
You can take an app compiled for 1.0 and it will run on a machine which only has 1.1 installed, whats more, you can run an exe compiled for 1.1 which has references to assemblies compiled for 1.0. That way you can migrate your 1.0 apps one assembly at a time. (If you need to)


>Sounds like *very* sound advice. Is it possible for multiple versions of the .NET framework to co-exist? Alternatively, can an app built, say, for version 1.0 run under 1.1? Just thinking ahead to the day when I have a client with existing 1.0 apps, that doesn't want us to deliver a 1.1 app for fear of breaking their existing apps.