E79 error

i will give you 2 solutions try both

1 solution:
1. Turn off the console.
2. Disconnect all the cables.
3. Disconnect The HDD.
4. Re-connect all the cables without the HDD or Memory Unit.
5. Turned the console back on and if the issue still persisted contact Microsoft because your console might need to be repaired.

2 solution:
Clear All Installed Game Updates and Console Cache
1. Go to the "system" blade
2. Select "memory"
3. Press Y on the HD symbol
4. Press X,X, Left Bumper, Right Bumper, X,X
5. A message will appear saying: "Do you want to perform maintenance on your Xbox 360 storage devices?"
6. Select Yes
Clear Any Failed system updates that cause the console to error.
1. With the console off, press and hold the sync up button (the small white one)
2. While holding the sync button press the power button to turn on the console
3. Continue to hold the sync button until the Console has booted up completely.
4. During the boot process the console should clear any failed updates, allowing you to use it normally.

This one work for me.
My box is up and running again
i did a video about this check it out http://www.youtube.com/watch?v=qTXw2RkSiMY