When you run Dcpromo, your receive one of the following:

Active Directory Installation Failed:                              The operation failed with the following error:                              The system cannot find the file specified.                               New Credentials.                              The operation failed with the following error: "Access is denied".                               These error messages can be caused by one or more of the following conditions:                               The absence of the default Ntds.dit file.                              Incorrect permission on the default Ntds.dit file.                              Incorrect permissions on an existing NTDS folder structure.
When you install a Windows 2000 server, regardless of the product or its role, a model Ntds.dit files is located at %SystemRoot%\System32. When you promote a server, the actual Ntds.dit file is created at %SystemRoot%\Ntds.

If you received the The system cannot find the file specified message, the %SystemRoot%\System32\Ntds.dit (default) file is missing. The simplest fix is to expand Ntds.di_ from any server CD.

NOTE: Check the %SystemFolder%\Debug\Dcpromo.log to see if this was the problem.

If you receive the Access is denied error, verify that the following permissions are set:

System32\Ntds.dit                               BUILTIN\Users:             Read \[RX\]                              BUILTIN\Power Users:       Read \[RX\]                              BUILTIN\Administrators:    Full Control \[ALL\]                              NT AUTHORITY\SYSTEM:       Full Control \[ALL\]                              Everyone:                  Read \[RX\]                               %SystemRoot%\Ntds                              BUILTIN\Users:             Special Access \[RX\]                              BUILTIN\Power Users:       Special Access \[RWXD\]                              BUILTIN\Administrators:    Special Access \[A\]                              NT AUTHORITY\SYSTEM:       Special Access \[A\]                              CREATOR OWNER:                                 %SystemRoot%\Ntds\Drop  (only if \Drop exists)                              BUILTIN\Users:             Special Access \[RX\]                              BUILTIN\Power Users:       Special Access \[RWXD\]                              BUILTIN\Administrators:    Special Access \[A\]                              NT AUTHORITY\SYSTEM:       Special Access \[A\]                              CREATOR OWNER:             Special Access \[A\]
NOTE: Check the %SystemFolder%\Debug\Dcpromo.log to see if this was the problem.

NOTE: After successful promotion, the following permissions should exist:

%SystemRoot%\Ntds                              NT AUTHORITY\SYSTEM:       Special Access \[A\]                              BUILTIN\Administrators:    Special Access \[A\]                              %SystemRoot%\Ntds\Drop                              NT AUTHORITY\SYSTEM:       Special Access \[A\]                              BUILTIN\Administrators:    Special Access \[A\]