Well, you will have to be a little more specific on how you flashed this 78. What type of SATA Connection are you using ( PCI, Motherboard/ VIA etc... ).
To say that your Elite will be totally useless is not in question.
If you have the original firmware from your 78, you can purchase a Hitachi or Samsung and replace it.
Other than that man, I would try to restore that original firmware you have. Is the drive not being detected in windows anymore? And have you hooked it back up to your 360 to make sure it doesn't work?
More information and help will be on it's way...