When you attempt an unattended upgrade of Windows NT 4.0 to Windows 2000, you receive:
The specified Setup script file (<path>\unattend.txt) is inaccessible or invalid. Contact your system administrator.NOTE: This error occurs with winnt32 /unattend:unattend.txt.
You are missing the UnattendMode=FullUnattended parameter in the unattend.txt file:
\[Unattended\] NTUpgrade=Yes UnattendMode=FullUnattended \[UserData\] ProductID="xxxxx-xxxxx-xxxxx-xxxxx-xxxxx"