Primary domain Controller

As this is the first step towards moving to a native WIN2K domain, make sure of your planning. You must be able to live with your root domain name as you will be unable to change it one you have migrated. Also, you should migrate at least one BDC toWIN2k DC in order to adequately maintain the mixed mode network. (You should have at least one other WIN2k Domain Controller available to move the Infrastructure Master role to) You should also correct ALL errors in the event logs on the PDC and perform a full synchronization through the domain controllers, then take one BDC offline and lock it away until such time you are SURE your migration is successful. At that point you will be able to blow out the locked away BDC and bring it up as a WIN2k DC. Remember to maintain your rollback path. An admin without a good plan better have a good resume.

Good Luck

Use Mixed mode, make sure you hve atleats one NT BDC, upgrade your PDC first, check it & then upgrade BDCs running SQL & Exchange.
Akash