Please disregard the notes here! The final solution to the problem of modfying the BIOS-flashing utility are better explained in the README file. Make a copy of the original image: cp usb1.img usb1.orig.img Use this to setup the freedos flashing image: losetup -o 32256 /dev/loop0 usb1.img The mount it: mount /dev/loop0 /mnt/usb The contents look garbled, but this works. Using losetup without the offset may not let you save files when editing. I tried using the pacth directly on the image file, but that doesn't seem to work. # native locked setup REM set BIOSVER=GE10208 # setups for using winXP or any linux distro set BIOSVER=XPWITHCD REM set BIOSVER=XPNOCD # setups for use with winCE REM set BIOSVER=CEWITHCD REM set BIOSVER=CENOCD The NOCD options are much faster to boot patch and diff: manually edit the autoexec.bat file after mounting then produce a binary patch with this command diff -a --binary usb1.orig.img usb1.img > flashrom-binary.diff (where usb1.img is the one you edited) The patch can then be applied to the original image file with: patch --binary < flashrom-binary.diff I finally just added the freedos edit.exe program to do the editing of autoexec.bat. This avoided the problems with unix-style line ending characters.