joeware - never stop exploring...

This is a nice article on Active Directory Limits

http://technet2.microsoft.com/windowsserver/en/library/d2fc40d8-50ba-450c-959b-28fd7e31b9961033.mspx?mfr=true

Summary

Max Objects - 2³¹ minus 255 or ~2.15 Billion or 2,147,483,394

Max SIDs - 2³⁰ or ~1 billion or 1,073,741,824

Max Group Membership for Security Principal - 1015 groups

Max FQDN Length - 64 characters

Max File Name Length - 260 characters [1]

Max OU Name Length - 64 characters

Max Group Policies applied - 999

Max Number of Directory Operations per LDAP Transaction - 5000[2]

(Recommended) Max Number of Domains - 800 (Windows 2000), 1200 (Windows Server 2003 FFL-2)

(Recommended) Max Number of Domain Controllers in a Domain - 1200[3]

[1] This is a bit tricky as this limitation is in the Win32 subsystem, not in NTFS which has something like a 64k limit. You can get around this limit if the tools you use use unicode path format with \\?\

[2] Wow, I have never been even close to that… I expect you would be close to if not over bumping the Max LDAP Packet size of 10MB (default)

[3] If over 800 DCs and using ADI-DNS, see KB267855.