All the games you've worked on are in the StencylWorks\Games folder, in individual folders listed by game name. If you save any/all of those folders (ideally, just zip up the entire \games folder) you can copy those files into any other installation of SW to access them.
There is also an extension for backing up your games to a separate location. Many people like to use a networked drive type service for backing up things. Dropbox is an example of one.
