I found my error in winpeshl did not have /s. And no, for programs with switches in winpeshl.ini, you must use a comma and the remainder of the command in quotes. For example, here is my full winpeshl.ini I am working with: [LaunchApps] %SYSTEMDRIVE%\Windows\System32\wpeinit.exe %SYSTEMDRIVE%\Windows\System32\setres.exe, "1024 768 32 1" %SYSTEMDRIVE%\Windows\System32\diskpart.exe, "/s %SYSTEMDRIVE%\Windows\System32\diskpart.txt" %SYSTEMDRIVE%\Progra~1\BurnInTest\bit.exe, "-x -r -c test.bitcfg" This issue is resolved.