Instructions
Go to the Xbox 360 dashboard. If your Xbox 360 is off, turn it on. If you're playing a game on your Xbox 360, click the button in the center of your controller, go to the "Settings" menu, scroll down to "System Settings" and press "A." This will take you from the game to the dashboard and allow you to skip to Step 4.
Scroll up or down to go to the "My Xbox" menu.
Scroll right to go to the "System Settings" menu, and press the "A" button.
Scroll down to go to "Memory," and press the "A" button.
Scroll down to go to "Hard Drive," and press the "A" button.
Scroll down to "Clear System Cache," and press the "A" button.
Select "Yes" and press the "A" button when prompted to confirm that you would like to "perform maintenance on your Xbox 360 storage devices" and continue. Wait for the updates to be removed and go back to the dashboard.