upgrading 2000 server to 2003 server

Getting this error when i run the adprep /forestprep command?

Any advice?


Adprep was unable to upgrade the schema on the schema master.
[Status/Consequence]
The schema will not be restored to its original state.
[User Action]
Check the Ldif.err log file in the
C:\WINNT\System32\debug\adprep\logs\20030707151100 directory for detailed
information.



Adprep set the value of registry key
System\CurrentControlSet\Services\NTDS\Parameters\Schema Update Allowed to 1



Adprep was unable to update forest-wide information.
[Status/Consequence]
Adprep requires access to existing forest-wide information from the schema
master in order to complete this operation.
[User Action]
Check the log file, Adprep.log, in the
C:\WINNT\System32\debug\adprep\logs\20030707151100 directory for more
information.





ERROR: Failed to transfer the schema FSMO role: 52 (Unavailable).