Halo 2 doesn’t work on my computer anymore.

I got Halo 2 for my laptop a while back before I got Windows 7. Before I upgraded my OS, I started getting this error saying that another Wndows LIVE application was running on my machine, which isn’t true. I’ve tried re-installing, updating, changing, renaming, and reemoving some files. Nothing is working and I’m really tired of not being able to play it. Please help me out. 🙂