When new version is installed and has chance to run, the old one has already been removed.
Using `roRegistrySection` is the way to handle this - e.g. say have a key `version` in it, on app launch check what's in it and if older, do whatever upgrade or notification needed. If key does not exist, it's first install of the app (or prior version that did not care about versioning). Then store the current version there.