Примерно так (не проверялось):
Код:
@echo off
setlocal enableextensions enabledelayedexpansion
for /f "tokens=3 delims= " %%i in (
'reg.exe query "HKEY_LOCAL_MACHINE\SOFTWARE\Multi Theft Auto: San Andreas All\Common" /v "GTA:SA Path"^|find.exe "GTA:SA Path"'
) do set sPath=%%i\gta_sa.exe
if defined sPath if exist "%sPath%" start "" "%sPath%"
endlocal
exit /b 0
