Imac started to slow down, then stopped booting. All I get is blank white screen. Took it to apple genius bar and they said I needed new hard drive, about $250 to fix. I took it for a 2nd opinion at a local shop, and they said I needed a new motherboard, about $800 to fix. So now I'm stumped. How can 2 reputable places say 2 different things? How can I figure out the real problem? I would like to get this fixed, as I have 0 working computers right now and I sell online so its imperative that I have one that works. I appreciate any help! Thank you!!