I've had my .NET Passport -> Windows Live ID for a very long time. Since that time, I've changed my primary email address and would really like to not have to use my email from highschool to still get access to everything in the Microsoft world. My MSDN account is tied to it, as well as SkyDrive and Xbox Live. Can I change my login email to use a different one, without having to start a new account? If so, what are the steps I need to take and places I need to go to get that changed globally for all of the Microsoft webapps that I use?
I think the best you can do is go to https://account.live.com/ and setup your new account as a linked account.
Linked accounts let you switch between account quickly by clicking on your name. You can log into any of the accounts and then switch.
One word... stuffed. You could try emailing support, but I think you are stuffed. I would like to know how you get on.
If you log into https://msdn.microsoft.com/en-us/subscriptions/manage/default.aspx and from hee there are links to send a request to switch your live id.
If you go onto your xbox and go to your account page you will see an option to chnage the live account associated with your gamertag.
For future proofing
I recomend buying your own domain (I own Hinshelwood.com) and using this as your live account. That way you can point it at any email account you like and keep the same address for life.
Just right click on the SkyDrive icon in your icon tray (lower right screen of your computer) and click on "settings". Then click the "unlink Skydrive" button. It basically logs you out of your old account and lets you login with your new one. When setting up the new email address, just click to keep the file locations the same on your computer and viola!
All your old files will be linked to your new email address!
The originally accepted answer from hcris is no longer accurate. Now (at least of 2014), you access your primary account login through Account Settings -> Aliases. Once you change your primary alias, you can then use it to log in to all your Microsoft related accounts.