Stopping the Teams App Starting Automatically on Windows

HelloTonyRedmond

There's another solution if you do not want to fight the registry. This solution is user based, not machine.
First of all, the user need to have admin privileges,
Then:

On Win 7, open the msconfig as ADMINISTRATOR by right clicking on it and selecting "Run as Administrator", on the startup tab unselect Microsoft Teams and Teams Installer.
Reboot and you are done.

On Win 8 & 10, on the search bar type "task manager" and run it as administrator by right clicking on it and selecting "Run as Administrator", then on the startup tab, disable Microsoft Teams and Teams installer (only if shows up).

The reason I mention the user need to have admin privileges it's because even if you run the msconfig or the task manager as administrator, does not pull all the process to the list, I test it, I have around 35 computers to administrate, and this solution worked on the 3 OS ( Win 7, 8 and 10).
Hope this can help you.