Today Dallas, TX #1 Good Morning- After about 3 days of trial and error I need help. Alittle background info. I have acquired what I believe based of internet research is a early 2007-2009 imac All in one unit, it has the black back panel (not the silver aluminium design). It has USB, RJ45, firewall, headphone jack in the lower right corner however NO THUNDERBOLT which leads me to believe its an early design. It has a very large screen but it does not boot. It powers on, chimes and after about 2 minutes I get the folder with the question mark which again reading says the mac cant find a boot disk. What I have done : Reset the PRAM, did this successfully holding down the command, option and P+R combo on power on. I have downloaded OSX El Capatian and created a bootable USB from the .dmg image file using my windows machine. I plugged in the usb into the mac and held down the 'c' key and it recognized the USB with a yellow usb icon on the screen and the arrow below the icon. I clicked it and it spun its wheels however after 2 minutes or so of loading I get the stop sigh / circle with slash through it. Upon more research seems that symbol means a firmware / hardware mismatch with the IOS (IOS wont support that version of mac. So I downloaded Lion and snow leopard and those again held the 'c' at bootup and those versions gave me the grey apple symbol after about a minute and a progress bar at the bottom but after another minute or so the apple symbol changed to the circle slash again. This is my first mac, but I am a IT admin so I just dont know enough about the mac to determine if this is hardware or software. For example if the hard drive is bad on this, could it cause that symbol ? I was under the impression even with a bad hard drive if you have a bootable CD or USB it should at least boot all the way to the desktop from that medium. Please help. I will send you a case of beer for anyone who can assist. I haven't opened it and do not know the history and before i start popping off the screen I wanted to ask here. Thanks in advance !