Hi all, we've been trying to do an adprep and we kept getting the very same error no matter how. We solved every dcdiag/gpotool/repadmin etc we encountered and finally ended up looking a the ldif file that adprep was trying to install: at the CN=default-Display,CN=401,CN=DisplaySpecifiers,CN=Configuration,DC=MY,DC=DOMAIN,DC=COM Adprep is trying to add to property "extraColumns" the value: telephoneNumber, ,0,100,0. and the terminating error is that the attribute can not be modified because it belongs to the system. ??. Then it all stops This is a personal translation from the spanish error, sothese might not be the exact words. Error ids: [Status/Consequence] Error message: Error(8239) while executing ""C:\WINNT\system32\LDIFde.exe" -i -u -f "C:\WINNT\system32\debug\adprep\logs\20060807134417\DisplaySpacifiersActionUpdateLdif.001.ldf" -j "C:\WINNT\system32\debug\adprep\logs\20060807134417" -s my.domain.com". Any help appreciated. thanks