[quote] I contact Microsoft support and they sent me here.[/quote]Sorry, but they told you wrong. Nobody here can help with that. Bungie doesn't even run the Halo series anymore. Your product key has nothing to do with signing into your Microsoft Account, though. I've never played Halo 2 Vista and I log into my account just fine. The two are unrelated. You might just have to re-buy the game since there's no way to verify you ever bought it in the first place. That's why they say not to lose the product key, you know?