Hello, I just bought a iMac 24in (MA877LL) at a garage sale that was not working. I have never had a mac only pc's running Windows. When I plug the mac in I hear a chime and sometimes the fan will run. The screen is grey with apple logo and a loading bar that starts to barely load, and a spinning wheel. After a few minutes of this it turns off. From what I have read sounds like the operating system needs repaired. The computer came without a keyboard or mouse, I did try to hook one to it but wouldn't work without being able to boot. Can I remove the hard drive and place in an enclosure? Then hook it to my regular windows computer as external drive to repair the operating system? Or do I need another mac to do this? Thanks for any advice.