Instructions
Check the front of your Xbox 360 after seeing the E68 error code indicated on your television. The matching code on your Xbox should be a single red light on the power button.
Restart your Xbox 360. The problem may have just been a random error and not anything serious with the console.
Shut your Xbox 360 off. Press the small tab on the hard drive bay and pull up. Use canned air to clean the Xbox 360, hard drive and hard drive slot to ensure no dust or dirt is interfering with the hard drive connection. Reinsert the hard drive into your Xbox 360. Reboot and see if the error code comes back up.
Turn off your Xbox 360 and remove the hard drive again if the error message shows back up. Turn your Xbox on without the hard drive installed. If there is no error message, there is a problem with your hard drive and it needs to be replaced. Otherwise, there is a system problem with the Xbox 360.