Is it possible to convert existing workspaces from previous Visual Studio versions into a solution within Visual Studio .NET?
Yes. By you opening the existing workspace, Visual Studio .NET will convert it into a solution for you so that you can start working with your old projects in the new environment.
What if I don't like the new IDE, can I still work with the old one?
You can't use previous versions of Visual Studio to build and debug new .NET applications; however, you can customize the interface to look very similar to previous versions of Visual Studio with the MDI interface and window layout.