Windows could not parse or process the unattend answer file for pass specialize

We’ve all see this classic error message when performing a Windows build ‘Windows could not parse or process the unattend answer file for pass specialize’


The issue here always applies to a problem with the unattend.xml file being processed at the time and it’s recommended to check the setupact.log and setuperr.log in the c:\windows\panther\unattendGC folder to discover what’s going on.

If you can’t access the CMD prompt via a Shift + F10 at this stage then reboot into WinPE and copy the files over to a network share.

I had the problem recently and although the setuperr.log file reported an issue with the Windows product key the actual issue was caused by the Post Install ‘Configure’ step in a MDT integrated Task Sequence being disabled. This step is used configure the unattend.xml file so if disabled caused this catastrophic effect.


Once re-enabled the problem went away.


  1. it is enabled but even though I’ve error. Trying to build Dell Latitude 5280 for windows 10

  2. This same error is happening now in my new organization, MDT heavy and integrated into SCCM. However, Ive created a cleaner TS and imported in a fresh w10 wim file from source older on ISO from VLC
    Have the unattend file option unchecked in the step. Never have needed to use it before since most config ive done is in the TS. I checked for both those logs in the panther dir and they were not present. any advice?

    1. in their TS theyre not using an unattend file, they are using a custom settings and configure ZTI. I have created a package with a working unattend.xml file, and spcified to use it with the same error message. I grabbed it and inspected the contents are the same as the settings I added under the apply windows settings stage.

      Ive gone as far as reimporting in a fresh w10 Wim file from VLC, created a new boot.wim from adk, redistributed the unattend package. same error…
      I am really at loss. Could it be an mdt setting enabled in the back end causing this? some type of hook calling mdt for other settings instead? I have mainly used CM only for imaging and have very little experience with MDT.

      Thanks in advanced.

      1. it’s usually a screwed unattend file. Check the setuperr.log I mentioned in the blog post. They should present you with errors to narrow down the problem

  3. I ran the Windows System Image manager on the unattend file to check for problems and found none. I have also speficied not to use it, and it gave me the same error. When browsing the panther folder I find no logs in unattend and unattendGC does not exist.

  4. I use MDT with a database for existing devices. Maps the mac address to a computer name. I got the error by stupidly adding the full name of the computer ie TEST-VER7.mydomain.somewhere. in the database.
    This far exceeded the allowed character limit of 15 characters.
    Because the name came in from the database it displayed the specialized pass error.

    1. I don’t use an unattend file to apply our Windows 10 images in SCCM but I still got this error. My issue was naming the PC with a “space” in it (I know better). I assume all “bad” names will cause this issue.

  5. i finnaly deleted the unattend.xml from my Virtual machine clone and sysprep finish without the catastrophic msg, thanks to all for your help

    1. “i finnaly deleted the unattend.xml”
      I have the same issue, We don’t use answer files and task sequence takes care of all. how did you delete the unattend.xml? did you remove from the GOLD wim file? if yes, is that before syspreping it up?

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