Last month I received an e-mail purporting to be from M$ to download the latest version of Windows Live Messenger. It contained links to do so. I of course did not. I reported it to abuse @ virgin.
I will always consider this as very suspect and would never use it. The abuse team did say it came from an M$ domain. I just deleted it.
Should I need to update/upgrade I would go to M$ and do it from there. The e-mail may well be kosher but I would never trust that method.