As it says in the question my Macbook Pro wont go past the loading screen. I have followed the suggested tips online to rectify the problem and it has not fixed it. I have been able to load the boot screen and it has given me the option of reinstalling the operating system but when I select it, it comes up with an error. I'm currently running Mountain Lion so I don't know if that makes a difference. I was able to install Mavericks but I didn't so am unsure if that makes a difference. Please help.