I recently bought a new HD and I installed OSX on it with no problems. I then erased my old HD with disc utility. Now I want to reinstall OSX on the old HD so I can use it as an external HD. When I insert the OSX disc nothing happens. Is there anyway I can to it while the HD is in the enclosure or does it have to be in the computer because for some reason the OSX start up isn't coming up when I put the HD in the computer.