
Go download ConfigMagic final. Inside you'll find some blank eeproms; if you have a 1.0 use the 1.0 eeprom, everything else use the 1.1 one.. (If you have a 1.6 those two wont work, but anyways..)
FTP the eeprom to the xbox's HDD in XOS. I hope your HDD is unlocked, or you'll need a new HDD as well... But anyways.. yeah, if you have a recent version of XOS2, go to eeprom tools and choose "Restore eeprom from BIN" If its not there, you'll need to upgrade your XOS first.
Once you choose that, navigate to the eeprom (If the HDD is locked and you couldn't FTP it to the HDD, burn it to a CD) and select it; when its done your xbox will be up and running again.