Last week I upgraded my MacBook Pro 15" Late 2011 to OS X Sierra. It updated fine and I shut it down to go to bed. The next day it had horizontal red lines on the screen and it would load and then it would stay at a white screen. I thought my hard drive was corrupted so I did the Option+Command+R to do the internet recovery. I completely deleted the hard drive using the Utility tool and reformatted it. Then I let it install overnight. The next day it was working. Since the recovery thing installed OSx Lion on it, I upgraded it to Sierra. Then I let it install its updates and downloaded and installed XCode and Google Chrome. It worked for two days and now today I turned it on to compile some code on Xcode and the horizontal red lines came back on and it would not boot again, it stayed on a white screen after loading half way. I turned it off and let it sit for a minute and then tried to do the Internet recovery again but then the red stripes were gone so I hard shut down and turned it back on and it booted. Does anyone know what could be causing it? I don't want to upgrade it yet because MacBooks are very expensive these days.