Configuring preferences and options in Outlook.com
Hi Philip,
Please be informed that, if your primary alias ends in @hotmail.com, @msn.com or @live.com, and you change it, you won't be able to make it primary again.
I would suggest you refer to Raymond P. suggestions from this link.
If the above link does not help, you may contact the Windows Live support.
http://windows.microsoft.com/en-US/windows-live/id-support
If you need any further assistance let us know and we would be glad to help you.