My Microsoft Account does not exist…

I am trying to login to a Microsoft account which have not used for over a year. This account appears to have been locked or closed as attempts to login return a message stating the account does not exist. Attempts to create a new account using the original username fail as apparently that name (an email address belonging to me) is already in use. I need to reactivate this account as it is linked to an MSDN subscription which I need to access. Please help, thankyou.