Instructions
Turn off the Xbox 360. Unplug the power cord.
Remove the hard drive by pressing the release button between the hard drive and the air vent. Lift the hard drive away.
Check the hard drive contacts for dust, dirt or other foreign substances. Clean if necessary.
Reattach the hard drive by inserting the back end of the hard drive into the hard drive bay on the Xbox 360. Press the front end into the Xbox 360 until it clicks.
Reinsert the power cord and turn on the Xbox 360. If the Xbox 360 still does not recognize the hard drive, the hard drive or Xbox 360 will need to replaced or repaired.