E68 is Voltage Error… This error means that the Xbox 360 has insufficent power to function properly. This can be caused by an error in the hard drive or the fans that make them suck up too much power, it can also be caused if you have unnecessary accessories attached to the console like an external fan unit.
To further check this error, u need to unplug all the USB connected accessories, following by hard drive.
In my case, the hard drive problem, once removed it, the Xbox 360 is UP and working fine.
The Xbox 360 HDD is using SATA 2.5″ Western Digital laptop HDD, connected via a special Xbox connector/adapter. I found out from Internet that the only thing that makes a 360 HDD unique from others is a special secure file system and sector. Therefore, we can essentially hack other hard drives to do the same thing. Below site provides the steps to do it.
Below is the features of Xbox 360 storage. Without the HDD, we can still play games~~~