After the Windows Setup and a reboot, the OOBE phase starts and the unattend.xml file is typically processed at this stage. The following message window may appear on some image deployments:
Windows could not configure one or more system components. To install
Windows, restart the computer and then restart the installation.
Missing below Windows Update inside the reference machine from which the image has been captured.
After the failed deployment of Windows, boot back into the KBE and open Recovery section to diagnose the failed deployment. Notepad/Review the C:\Windows\Panther\setuperr.log and confirm you can see the same or similar error as described in the below Microsoft KB article.
Install the following fix on the reference machine and re-capture it: http://support.microsoft.com/kb/2685811
After re-capturing and re-deploying the image, you should not run into the error mentioned above.
More information can be found here: http://en.community.dell.com/techcenter/os-applications/w/wiki/2560.client-operating-system-deployment-known-issues-and-work-arounds