My MacBook Pro has been acting very slow lately (15 minute boot-ups, slow to open any application, rainbow ball showing up at practically anything I try to do). On top of that, the Mac would freeze when I opened System Preferences (desktop and screensaver) or iPhoto. So I finally decided to do a fresh install of Mountain Lion. The install was successful. However once I restarted the computer, it took a full 15 minutes for the login screen to appear. Of course, the rainbow ball followed soon after login. Opening any Application takes forever as well. Does anyone have any ideas as to what may be causing this? I ran disk utility before the install to repair any bad parts of my hard drive. It said it was successful. So what exactly is going on? This is a clean install and I haven't even added any of my files that I had backed up.