one or more user have itunes installed on this computer

The full text of the error message, and what exactly you did that triggered it, would help, but it does suggest a potential clash. There are two main versions of iTunes, one available as a direct downloadable installer from apple.com that can be installed for all users, or the current user, and another from the Microsoft Store that I think installs for the current user, but not absolutely certain on that score. Multiple versions may not play nicely together and can complicate the process of updating iTunes. In general iTunes can only be opened in one profile at a time so when switching users there can be problems if iTunes hasn't completely shut down in the other profile.

tt2