You could attempt a social engineering play, if you're really that curious to know...
Call up microsoft, claim to be the owner of the account who needs help with a problem, they should ask for your name, claim it was registered for you by a relative as a xmas present or something, but you don't remember which, if they could give you the first name, or the initials as a hint so you can contact them for the rest of the info you need.
Sort of a long shot, but if your SE skills are on point you could probably get a little something out of the support person.