Instructions
Restart the Console
Press the "Power" button on the front of the Xbox to turn it off.
Press the "Power" button again to turn the console on.
Confirm that the "E74" error is displayed. If the error does not appear, no further troubleshooting is required.
Submit a Console Repair Request
Visit the Xbox Online Service Center.
Click "Start a Repair Request."
Log in using your Xbox Live account information. If you don't have an account, click "Create Membership" and follow the instructions.
Click "Start a Repair Request."
If prompted, complete the "Register a Product" form.
Follow the instructions to submit your service request and mail your Xbox to a repair facility.