I had the same error trying to create my own unattended cd, but i found a tool called "RunWPI" in WPI page, this tool makes run your WPI and Runonce. 1. You need to edit the last lines of Winnt.sif with bloc notes, delete where says something like WPI.hta. 2. Copy RunWPI.exe to $OEM$ folder and modify the cmdlines with only this: [COMMANDS] RunWPI.exe 3. Thats it !!!