+ 0 Votes Trust shasca 4 years ago If you get any kind of AD error when joining a new PC the chances of it have full trust to the domain are pretty slim. Try running sysprep of said PC and see if the error goes away. There is also a tool called Newsid that reworks PC info a new. http://support.microsoft.com/kb/302577 http://technet.microsoft.com/en-us/sysinternals/bb897418.aspx + 0 Votes GUID is duplicated, not the SID mancalledSun 4 years ago When you say "try running sysprep" I take it you mean, rebuild the PC with our corporate image? That is exactly what I am trying to do, but when a name is given during the 1st step of the RIS process it finds a duplicate GUID reference (somewhere) in AD, not a duplicate client name or duplicate SID. I could carry on regardless, but do not want to risk knocking the other machine of of the domain (if indeed this is what will happen). That's what I want to know.