Creating alternate realities in your virtual machines

Suppose you need to test certain software package, but aren't sure if you will want to leave it installed in your computer because it could cause conflict with other similar software packages. For example, let's say you use the Mozilla Firefox web browser in your daily chores, but want to try out the new Google Chrome web browser. You could create an alternate reality where you'd uninstall Mozilla Firefox and install Google Chrome and, if you don't like what you see, you can revert those changes to make Google Chrome disappear and Mozilla Firefox reappear as if nothing ever happened!