Things You'll Need
Instructions
Power on the Xbox 360 and open the disc drive to see what model is installed (see the second Reference link below). The Phillips drive cannot be flashed.
Download the appropriate firmware for your brand of disc drive (see the second Reference link, then the first Resource link). Download and install a DVD burner program. Drag and drop the firmware files to the DVD burner program and insert a blank DVD into the drive. Burn the boot files to the disc and leave it inside your computer. Turn off the computer.
Use a Torx screwdriver to remove the screws holding the Xbox together. Pull off the faceplate then remove the side panels by inserting a thin screwdriver into the holes and prying the panels apart.
Unplug the thick SATA cable from the Xbox DVD drive. Replace the cable with a new cross-wired SATA cable that connects the Xbox drive to your computer's SATA port.
Touch the two exposed wires on the SATA cable together while pressing the Xbox "Start" button. Pull the wires apart when the green Xbox light flashes.
Restart your computer and let it boot from the DVD disc inside. It will automatically flash the Xbox.
Reassemble your Xbox 360, replacing the original SATA cable into the Xbox DVD drive.