This one crops up from time to time. You need a Microsoft LiveID for use with say Windows Messenger. But when you go through the sign up process, you only have options for a .hotmail.com or .live.com domain on your alias.
If you have registered your own domain name, then ideally you want your LiveID profile to be somehow linked to that as well.
Turns out it is pretty simple. There are many ways to get to the right place, here's one:
Go to Microsoft.com
Scroll down to the bottom of the page
Click on Manage my profile
Click on Sign In up the top right
Click on Create new LiveID
And there you are – you can add your own email address.
Use this with Windows Messenger and all the other Microsoft Live services.