Error message when you run the Prep Schema step on the locked-down Active Directory service for the installation of Communications Server 2007: "Either a required impersonation level was not provided, or the provided impersonation level is invalid"

When you run the Prep Schema step on the locked-down Active Directory directory service for the installation of Microsoft Office Communications Server 2007, you receive the following error message:

This issue occurs because the Communications Server 2007 deployment tools do not have the impersonation level that is required to access the following registry key value on the locked-down Active Directory service:

To resolve this issue, run the Prep Schema step on a domain controller that has the Schema Operations Master role.

To determine which domain controller has the Schema Operations Master role, follow these steps:

1. Click Start, click Run, type mmc, and then click OK.
2. On the File menu, click Add/Remove Snap-in.
3. In the Add/Remove Snap-in dialog box, click Add on the Standalone tab.
4. Double-click Active Directory Schema, click Close, and then click OK.
5. Right-click Active Directory Schema in the upper-left pane, and then click Operations Masters to view the server that has the Schema Operations Master role.

Note The Active Directory Schema snap-in is available only after you register the Schmmgmt.dll file. To register the Schmmgmt.dll file, click Start, click Run, type regsvr32 schmmgmt.dll, and then click OK. A message may appear that states that the registration is successful.