Teams is now included in Office ProPlus installations for Office 365 users. However, not everyone wants or needs to use Teams. Here’s how to stop Teams being installed or starting automatically each time a PC boots. You don’t need this information if you’re one of the 19 million people who use Teams, but you might just not be in that category…
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.
@DanielAlegria That kinda-sorta-works until the next time you use Teams. Then it resets that flag and Teams wants to load every time I reboot. I want to Permanently disable Teams from starting when I reboot. I need it every once in a while, not everyday.