Sorry - should have clarified, my SME server can be part of my domain for DNS purposes (begins with numeral) but I have a security domain (Windows 2000) that I wanted SME to join. In 6.01 and 6.5 (haven't tried 7.0a yet) you are prohibited from joining a Windows security domain unless the "workgroup" begins with a letter.
Should've been more clear and thank you for the reply.