My Hotmail/Outlook account has disappeared

I have received the message "That Microsoft account doesn't exist."

This is despite the account being used regurlarly.  If I try to set up a new account with the same name I am told "That name is already in use"  How can it not exist and be in use at the same time?

 I have a number of folders/attachments in Outlook which I need access to desperately. 

Can anyone please help?