|I'm not sure what you mean by rebooting into Standalone mode so that that machine won't connect to the Domain. It's not a matter of booting, but of logging on properly.|
Did you setup these computers and the Domain? If so, Chris is right, but you need to do a few more steps. After logging in locally, you need to remove the Domain login option from the client. Then, reboot, and add the client back into the Domain. Reboot again, and you should be able to login to the Domain. If you're not sure how to do this, then find another Domain Administrator who knows how to manage Domain computers.
Life's more painless for the brainless.