But you could do it on Windows NT and Windows 2000.

You could switch back and forth between "Workgroup" and "Domain" all you wanted without having to create a new box account. As long as the sysadmin didn't delete the box account from Server Manager, it would just re-use the box account.

Sure, if the workstation and server got the box account hashes desynchronized it would be a problem. For instance if you create an image of the box, and the account hash gets updated a week later, then two weeks after that you restore the image (with its stale client-side hash), then you'd have a problem.

But that's not what I'm talking about here. I'm saying:

- User is already in the domain. Box has perfectly good box account on the domain with perfectly good hash.

- User clicks "Workgroup". Welcome to the workgroup.

- User clicks "Domain". Do you want to create a computer account for this box now? No. Welcome to the domain.

That worked on NT/2000. On XP you don't get that last option, it forces you to enter an administrator's password.