You can certainly keep your media files and project files. The upgrade will not affect them.
However, as I explain in my books, it's NEVER a good idea to open an older version project file with a newer version of the program. This would be particularly true if you were trying to open a version 2 project in version 9. It nearly always causes corruptions and buggy behavior.
It's best to keep version 2 of the program on your computer and finish any version 2 projects in it. Use version 9 for starting new projects.
I finally finished old projects, installed Premiere 9 and started on new ones. A question that I can't seem to get an answer for so far: I've added multiple tracks to make a music video. Any suggestions on how to work with visualizing multiple tracks. To view each individual track in the monitor panel or switch between tracks, I use the enable feature. I know there has to be an easier way. Will adjusting the transparency or opacity help?
The professional version of Premiere includes a tool for cutting between several tracks of video -- cutting between, for instance, several views of the same scene.
Premiere Elements does not. In Premiere Elements, you just need to manually work with your video tracks.