Hi Jamie,
Welcome to Laptop GPS World.
You may have several versions of Microsoft Streets and Trips installed on your laptop computer at the same time. I like to keep my existing version when installing a new version. That way I'm able to compare the new software to the old software, the new maps to the old maps, etc. After you are certain that you just want to keep the new, you may uninstall the old.
Make a backup copy of all you old saved Streets & Trips files. When you open in a new version a Streets & Trips file saved in an older version, you will be prompted to let the program perform a conversion to new version format. When you click OK, and when you subsequently save the file in the new S&T version, there will no longer be a way to open the file in the old version of the program. That is the reason for the back up.