I have just downloaded and installed Adobe Photoshop Starter Edition and used it to view pictures in one folder. Now whenever I start up the program, that folder and all of its pictures come up by default. How can I stop this behaviour?
You are misunderstanding the function of this program. It creates a catalog of images, which may be located anywhere on your hard drive, in any number of folders. That catalog is opened when the program is started. You can remove images from it [DEL], but it is better to learn what the program can do.
Most users have catalogs of many pictures [thousands typically]. They find what they want by filtering that view, whcih you can do in a multitude of ways. Time/date is one. Using the tagging feature is the most powerful.