ive never went back orig in my v78 but in toolbox there is a pull down that says restore. i know it can be done just look around it some were.sorry i cant help more.
this should help
Upgrading From Older Firmware?
If you are upgrading from an older hacked firmware, like a previous GaryOPA firmware, a Birdy firmware, or the original Commodore4Eva package, you must restore your drive to the original firmware before continuing. If you are flashing the firmware to a stock drive, ignore this section and skip to “Flashing The Drive.â€
Right-click on the X-LG folder and select “Open Command Window Here.†A command window should open up.
Type in the following command and hit Enter:
RESTORE.BAT X
Where X is the drive letter of your Hitachi drive.
It will restore the firmware back to the original. This is necessary before flashing to the latest firmware. After restoring the firmware, it is probably a good idea to disconnect the SATA cable, power off the Xbox 360 and PC, then continue the process of getting the drive into ModeB before flashing with the updated firmware.
got it from here
http://www.360mods.net/Downloads/details/id=61.html