Halo 2 on PC keeps launching

Hi everyone. Need some help on an issue with Halo 2 on PC. I searched everywhere on the internet and on this forum but I can’t seem to find anyone with my same problem, in case I haven’t searched well, please notice me so.

Basically I installed Halo 2 without any problem whatsoever. Now, every single time I launch Halo 2 and then I stop playing, the game keeps launching itself endlessly, no matter how many times I force it to quit in task manager, no matter how many times I close it manually from inside the main menu. I also have Halo CE installed and after I close it, even in that case Halo 2 launches itself. As a matter of fact, even while it’s running, Halo 2 keeps launching itself because every minute or so I get this pop-up message that says “Halo 2 is already running on this machine”, and after a while this messages start to stack up. It makes no sense to me, and I couldn’t find any solution. Of course to stop this I could reboot the PC, but come on, should I really do this every time I stop playing? There has to be a solution.

Does anyone know what’s the matter with it and how to solve it?

Keep in mind that english is not my first language so excuse me for any mistake.
Thanks to everyone that would help me out.

I didnt’ know that halo 2 exists on pc

It does, I think it was released something like three years after the original Xbox version but it was an exclusive for Vista OS. I heard many complaints about the difficulties in installing it on modern systems but I had none.

I had the error too, I reinstalled and that seemed to fix it. If I remember correctly I also set the installer to not start the game when finished so maybe that’s where it glitches?

After having the problem myself, I (think) i managed to solve it by moving startup.exe in the Halo 2 folder to a different location, i guess you can also delete it.
I will update if the issue keeps occurring after this potential fix

Edit: It has solved the problem for me at least, the game has not launched itself since.