I have a Intel based MacBook Pro that recently had a hard drive go bad. I replaced the hard drive. My DVD Drive is also bad. I put an .ISO of Mac OS X On my external hard drive, hoping to boot from that to reinstall Mac OS. I plugged in the external hard drive, restarted the computer and held the "option" key as instructed by Apple's knowledge base. Instead of the folder with a question mark on it, I do get an arrow, but nothing else. Will it not boot because it's an ISO and wasn't "burned" to my external HD? Any help is much appreciated. None of my copies are illegal or counterfeit either, before I am asked.