Gentlemen:
When trying to do Windows 2008 ForestPrep (adprep /forestprep) on my 3 DC network I kept getting an error message denying Schema updates due to one of the domain controllers (A virtualised DC acting as an AD backup and Enterprise Root CA) being more than 180 days old and thus causing that annoying tombstone issue.
I was able to FORCE override my Schema Master to be updatable anyways (to allow installation of Windows Server 2008 into my domain) by manually changing the following registry keys under HKLM\SYSTEM\CCS\Services\NTDS\Parameters:
Added the "Allow Replication With Divergent and Corrupt Partners"=1 DWORD key.
I also manually changed the following keys: "Schema Delete Allowed" to 1, "Schema Update Allowed" to 1, "Strict Replication Consistency" to 0.
The last 3 keys only exist on the Schema Master. Of course I'm doing this on my experimental network.
(I should mention I did this on my experimental home test network so I wasn't quite sweating bullets as I might have trying it on a company's production network!)
Regards, Anthony Maw, Vancouver, Canada, anthony@maw.bc.ca, (604) 318-9994