When you use the Microsoft Windows Pre-installation Environment (WinPE) and the Diskpart tool to deploy a Windows Server 2003 image, and run Winnt32.exe, you receive:
No valid system partitions were found. Setup is unable to continue.
If you ran Diskpart before Winnt32.exe, you will receive this message.
To fix the problem, edit your batch file or installation script, and add the /syspart:X: parameter to the Winnt32.exe command.
NOTE: X: is the drive letter of the partition you want to install Windows Server on.