The Windows group has its own domain (known as NTDEV for historical reasons) which operates separately from the domain forest operated by the Microsoft IT department. Various trust relationships need to be set up between them so that people on the Windows team can connect to resources managed by the Microsoft IT department and vice versa, but it generally works out okay.

There are some glitches, but that's the price of dogfood. What better way to make sure that Windows works well in a cross-forest environment than by putting the entire Windows division in its own domain separate from the rest of the company?

Subject: Newbie domain join question

My user account is in the REDMOND domain. Should I join my machine to the REDMOND domain or the NTDEV domain?

I was much amused by this cynical recommendation:

Subject: RE: Newbie domain join question

It's pretty simple, really.

If you want to have trouble accessing NTDEV resources, then join the REDMOND domain.

If you want to have trouble accessing REDMOND resources, then join the NTDEV domain.