Ok guys I have a 2007-08 MacBook Pro 15 inch 2.4 duo core processor 4 gigs of ram 500 GB Hard drive was running El Capitan not very good!!! Then wouldn't boot up! Took it to a local repair shop bad decision from the run around I am getting. Was told the HD has bad sectors advised to get new HD so I instructed him what I wanted new HD with a clean install of El Capitan. Nope the guy did a clean install of Yosemeti! So the confusion continues he has it for over two weeks the Holidays etc. Says he cannot get a clean install of El Capitan but did originally get a clean install of Yosemeti. But then now tells me possibly a bad mother board but he gets it running with Yosemeti not the other OS?? Hmm my thoughts are to do a clean install again with Yosemeti and see if I can salvage what I have or sell it for parts etc Am I getting the run around from this guy?? Called another PC & Mac repair shop they tell me El Capitan is the worst OS that Apple brought out & I tend to agree with them. But then told oh we can do a free diagnosis and tell you if the mother board is fried out or not!!! So if my MacBook is DOA I will be looking for another laptop oh well life goes on!!!