Fix GUID error 0X8009480E in Windows AD prep

You're migrating to a newer domain controller—maybe Server 2012 R2 or 2016—and you run adprep /forestprep on your schema master. Everything looks fine until you check the output or event log and see: Adprep encountered a GUID error (0X8009480E). The operation fails with something like "The GUID of the object is not consistent with the schema."

I saw this most recently with a client running a Server 2003 R2 SP1 domain controller as the schema master. They were trying to add a Server 2012 R2 DC. The error fired off because the schema master's Active Directory schema version was lower than what adprep expected for the extended schema attributes it needed to update.

In plain English, adprep tries to modify an object attribute called extendedSchemaInfo by its GUID. If the schema version on that DC is too old—specifically anything below version 30—the GUID doesn't match what adprep expects. It's not corrupt. It's just that the schema master hasn't been updated to support the bits that newer adprep versions need. Microsoft fixed this in later service packs, but if you're on SP1 or earlier, you'll hit this wall.

The real fix: update the schema version manually

Don't bother with reinstalling the OS or promoting a new schema master from scratch—that's overkill. You need to bump the schema version on that DC to at least 30. There are two routes. Pick the one that matches your environment.

Route A: Install the latest service pack (if possible)

If your domain controller can handle it, slap on Server 2003 SP2. That raises the schema version to 30 or 31. Reboot, then re-run adprep /forestprep. Nine times out of ten, this kills the 0X8009480E error.

But here's the catch—sometimes you can't install SP2. Maybe it's a critical production DC that can't be taken down for a service pack. Or maybe the hardware is ancient and SP2 breaks something else. In that case, go Route B.

Route B: Manually import the schema updates via LDIFDE

This is what I did for that client. It's more surgical and takes about 15 minutes.

1. Log into the schema master with Domain Admin and Schema Admin privileges.
2. Open an elevated command prompt.
3. Run regsvr32 schmmgmt.dll to register the schema management snap-in if it's not already registered.
4. Open MMC, add the Active Directory Schema snap-in. Right-click the root, and select "Operations Masters…" to make sure this DC is the schema master. It should be.
5. Right-click "Active Directory Schema" again, choose "Reload the Schema." This refreshes the cache.
6. Now we need to update the schema version. On your new server (the one you're trying to add), find the %systemroot%\system32 folder. Look for a file called sch14.ldf (or sch15.ldf, sch16.ldf—the number corresponds to the schema version). If you're targeting Server 2012 R2, it's sch14.ldf.
7. Copy sch14.ldf to the schema master. Put it in a temp folder like C:\temp.
8. On the schema master, run this command:
   

   ldifde -i -f C:\temp\sch14.ldf -k -j .

   The -k flag continues on errors (skip trivial ones), and -j dumps a log in the current directory.
9. Wait for it to finish. Check the output file—usually .log—for any "Add" errors. Ignore warnings about duplicate entries. If you see an error about "Access denied" or "No such attribute," something else is wrong (probably permissions).
10. After the import finishes, confirm the schema version. Open ADSI Edit, connect to the Schema partition, find cn=Schema,cn=Configuration,dc=yourdomain,dc=com. Look at the attribute objectVersion. It should now be 14 or higher on the major version (that's 14 for Windows Server 2012 R2 schema).
11. Now run adprep /forestprep again. It should complete without the GUID error.

If it still fails

If the error persists after the LDIFDE import, check two things:

• Is the schema master actually the schema master? I've seen setups where the FSMO role holder was seized or moved but the old DC still tried to act as the schema master. Run netdom query fsmo to confirm.
• Is the schema version actually higher than 30? Sometimes the LDIFDE import fails silently if the file path is wrong or the file's corrupted. Re-download the LDF file from the new server's installation media (look under \support\adprep).
• Check the application event log on the schema master. Look for event ID 1106 or 1107 from source SAM. Those tell you if the SAM database can't find a matching GUID. If you see those, you might have a corrupt schema partition. In that case, you're looking at a metadata cleanup or a forced demotion of the schema master—but that's rare.

Bottom line: 0X8009480E is a version mismatch, not a corruption. Update the schema version, and you're golden. That client of mine went from hitting the error to having the new DC join the domain in under an hour.