Instructions
Turn on your Xbox 360 Console and select "My Xbox." Select the "System Settings" menu.
Select the "Memory" tab on the "System Settings" menu. Pick any storage device that you would like the contents to be erased and press "Y" on your Xbox 360 controller. The memory cache of all storage devices will be emptied.
Press "Clear System Cache" under the "Device Options" section and select "Yes" when prompted to continue. You can also press in order: "X", "X," the "Left" bumper, the "Right" bumper, "X" and "X" to clear your Xbox 360&'s memory cache.
Wait for your system&'s memory cache to be cleared from all storage devices.