Darren,
the Reg Key is IncludeInheritedRights. It is documented on Page 53 of the Version 6 Admin Guide (http://ftp.support.veritas.com/pub/support/products/Exchange_Mailbox_Archiving_Unit/277778.pdf). It's got a "Legacy Name" so I guess version 6 can apply it within the Admin Console rather than you having to stick in a registry key.
Helpfully the manual doesn't tell you where to put the key if you aren't at ver 6 yet and there doesn't appear to be any other documentation. How unusual.
HKLM\Software\KVS\Enterprise Vault\Agents.
It's a DWORD. 1 = include them (don't do this!) 0 = don't (but this should be the default EV behavior anyway)
So there you go. You only need apply this if you think EV might be exhibiting bug behavior.
Hope this is helpful
David
http://messy.bravehost.com/