Instructions
Select "My Xbox" from the Xbox 360 console, then click "System Settings."
Select "Memory."
Select the storage unit containing the modified data. If this is the console's internal drive, select this. If it's a USB storage device, select this. Press "Y."
Click "Format," then confirm the action by selecting "Yes."
Enter the console's serial number, located on the back of the console, for confirmation. Click "Done" to complete the process. It should take only a few minutes to reformat the storage device. Once complete, all hacks and modifications should be removed and your "Call of Duty 4: Modern Warfare" game is restored to its original settings.