How to use Legacydn.exe to correct Exchange organization names or Administrative Group names in Exchange Server 2003 or in Exchange 2000 Server

Check out the folloing link, it gives the basic direction on how you can modify the legacyExchangeDN value.

http://support.microsoft.com/kb/324606/en-us

Please note:

Microsoft only supports using the Legacydn.exe tool only in a lab environment. The tool works only in an environment that uses a single domain controller.