Hay un fichero .bat por ahí rulando, que se usa para convertir la bios de 256 a 1024, prueba a convertirla , te reescribo el fichero, copias , pegas y grabas como .bat :
@echo off
set TITLE="Making a 1024K BIOS for Xbox out of a 256K BIOS for dummies"
echo.
echo CONVERTER BY TIKITOK
if "x%1"=="x" goto _syntax
set bios256k=%1
set bios1024k=bios1M.bin
if exist %bios256k% goto _256kpresent
goto _256kmissing
:_256kpresent
echo.
echo 256K bios found ( %bios256k% )
if exist %bios1024k% goto _fileexist
:_afterfileexist
echo.
echo Making bios now.
echo Please wait...
copy /b %bios256k% + %bios256k% + %bios256k% + %bios256k% %bios1024k% > NUL
if %ERRORLEVEL%==0 goto _success
goto _failed
goto _end
:_success
echo 1024K bios completed ( %bios1024k% )
goto _end
:_failed
echo Failed to create the bios.
echo check read only attribute of the 1M file ( %bios1024k% )
echo and the permissions you have (if any) on the 256K one ( %bios256K% )
goto _end
REM bios source is missing - display message and go away
:_256kmissing
echo cannot find %bios256k%
echo aborting...
goto _end
:_fileexist
echo.
echo WARNING WARNING WARNING
echo 1M bios already exists.
echo WARNING WARNING WARNING
echo.
choice /C:YN overwrite %bios1024k% file
if %ERRORLEVEL%==2 goto _nocleanup
if %ERRORLEVEL%==1 goto _cleanup
:_nocleanup
echo aborting...
goto _end
:_cleanup
del %bios1024k%
goto _afterfileexist
:_syntax
echo.
echo You are not using this file properly.
echo syntax:
echo %0 256kbios.bin
echo.
echo Or use drag and drop, and drop your 256K bios onto the
echo icon of this program.
echo.
goto _end
:_end
echo.
pause
Un saludo.
