The MASM Forum

IsWinPE is a tiny tool to detect if the user is operating under Windows PE ( Preinstallation Environmet ) or Windows. The environment variable ERRORLEVEL is set to 1 if WinPE is detected. Otherwise, ERRORLEVEL is set to 0

test.bat :

IsWinPE.exe

@IF %ERRORLEVEL% == 1 ( @echo Operating in WinPE environment

                      ) ELSE (
                              @echo Operating in Windows environment
                             )

Here is the 64-bit version.