Go to the "System" tab, then "Memory". Press Y for device options, then press either LB, RB, X(2), LB(2), X(2) or X(2), LB, RB, X(2), LB, RB. You will get a message stating that the system is performing maintenance.

Go to the Xbox 360 Dashboard with no game inserted. Scroll all the way over to "System" and select "Memory". When in the "Memory" screen, press Y and it will open the screen. Press X(2), LB, RB, X(2). You will get a confirmation screen asking if you would like to have maintenance done on your hard drive. Press A to confirm your choice. This will not erase anything on your hard drive.