>Can I run/develop a .NET app using the 2.0 Framework if it was written using a previous version of the Framework?

When you attempt to load a 1.1 app in the IDE you will be asked to convert it. This is great and I have done it many times. The problem Jay is if you are learning some things will be organized differently. For instance there are now partial classes and the designer will not move stuff form an older app to the partial classes. Just be aware you will see things differently than if you create it with 2.0.

By the way, if I understand things correctly a 3.0 is not a new version of VS but rather more like an add on. That is why Craid said what he did. The 2.0 stuff is still the same.
Tim