Hola Yo tengo el mismo problema, no se si Juan Carlos lo resolvio, pero aqui esta el log cuando ejecuto adprep32.exe /forestprep en mi windows 2003 server enterprise sp2 para migrar todo al windows 2008 server enterprise RC2
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Adprep created the log file ADPrep.log under C:\WINDOWS\debug\adprep\logs\20100308182453 directory.
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Adprep copied file C:\adprep\schema.ini from installation point to local machine under directory C:\WINDOWS.
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Adprep copied file C:\adprep\schupgrade.cat from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\PAS.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch31.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch32.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch33.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch34.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch35.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch36.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch37.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch38.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch39.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch40.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch41.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch42.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch43.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch44.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch45.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch46.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\sch47.ldf from installation point to local machine under directory C:\WINDOWS\system32.
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Adprep copied file C:\adprep\dcpromo.csv from installation point to local machine under directory C:\WINDOWS\debug\adprep\data.
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Adprep successfully made the LDAP connection to the local Active Directory Domain Controller NEPTUNO.
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Adprep was about to call the following LDAP API. ldap_search_s(). The base entry to start the search is (null).
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LDAP API ldap_search_s() finished, return code is 0x0
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Adprep successfully retrieved information from the local Active Directory Domain Services.
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Adprep successfully initialized global variables.
[Status/Consequence]
Adprep is continuing.
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ADPREP WARNING:
Before running adprep, all Windows 2000 Active Directory Domain Controllers in the forest should be upgraded to Windows 2000 Service Pack 4 (SP4) or later.
[User Action]
If ALL your existing Windows 2000 Active Directory Domain Controllers meet this requirement, type C and then press ENTER to continue. Otherwise, type any other key and press ENTER to quit.
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Adprep was unable to check the forest update status.
[Status/Consequence]
Adprep queries the directory to see if the forest has already been prepared. If the information is unavailable or unknown, Adprep proceeds without attempting this operation.
[User Action]
Restart Adprep and check the ADPrep.log file. Verify in the log file that this forest has already been successfully prepared.
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Adprep encountered a Win32 error.
Error code: 0x3a Error message: El servidor especificado no puede ejecutar la operación solicitada..
Alguna idea ??