Instructions
Turn on your Xbox 360 and access the "System" blade in the dashboard. Select "Memory" and press Y on your Xbox 360 controller to open the "Device Options" menu.
Press the following sequence of buttons using your Xbox 360 controller: X - X - LB - RB - X - X. Upon pressing these buttons, you will be asked if you would like to perform system maintanence on your Xbox 360 hard drive. Select yes to perform maintenance and delete all game patches.
Insert an Xbox 360 game to ensure that the patches have been deleted. Reinstall any other patches that you did not wish to be deleted using Xbox Live.