Hi All, Please forgive length of post - novice at explaining technical stuff. Late 2011 17" MBP / 2.4Ghz Intel Core i7 / 16GB 1333Mhz DDR3 Ram (Crucial Brand) Running Mavericks 10.9.5. Hi All, I am a light user - pretty much just use the MBP for web surfing, emails & word stuff etc but I rely on it heavily. It was replaced by Apple after the Early 2011 had Graphics issues & has shown no issues up till now. I normally just have Apple mail on all the time & Safari with about 6 tabs. Average temp is around 44- 55 degrees. A couple of days ago, I opened up Google Sketch Up (used for many years & never had a problem before) & this is where the problem started. Sketch up got stuck at opening itself & its pages up & locked the computer fully. The screen showed pages being zoomed in & all sorts of bad image tearing. Soon after, the fans kicked in big time & the thing started to get extremely hot. I thought it might resolve itself & waited for as long as I thought might be a good time but it would not resolve. Eventually, I got scared at how hot it got & tried shutting it off at the power button - it took 3 presses for it to shut down. I waited for it to cool down fully & did a restart. It took quite some time starting with a dark grey screen & then a light one but this time it has purple & light blue vertical stripes - these remained for quite some time & again the MBP started getting very hot with fans running high. Finally the screen went black but with fans still running. I waited some time but then shut if down manually again - same as before, it took 3 presses of the power button. I did this 2 more times but with exactly the same results each time. I aimed a high powered fan at the top of the MBP & a large ice gel pack covered in a towel underneath to mitigate against the heat each time. Someone told me about the Apple Hardware Test by pressing "D" on start up so I tried that & I opted for the "extended testing". It took an hour & 15mins but it reported back as "No Trouble Found" - see pics attached. Somewhat heartened by this, I then rebooted the MBP but unfortunately, the exact same issues were still in place & I was convinced my MBP was ruined. I tried a 2nd time but no change - differing grey screens followed by the vertical purple & blue stripes, high temps & then a black screen so I shut it off but this time, I *think* (not sure) it may have shut down with just a single press of the power button. This time I fully resigned myself that I was out of luck & very upset, just took a break. Some time later, just out of repetition, I started the Mac again - same issue as before light grey screen with issues, darker grey screen with issues, no inputs accepted, Purple & Blue Stripes, High heat & fans followed by a black screen. I do not know why, but for some reason (probably despondancy), I just let it stay this way (at the final black screen stage) & after about 20-25 minutes, the black screen went away, the fans slowly started to wind down & the normal log in page appeared but without those horrible vertical stripes. I was able to log in & the screen was back to normal but operation was a bit buggy - this has improved to what appears to be normal now. I noticed that my Macintosh HD icon showed that I gained about 8-9 GB's so I do not know what has happened there or what has been lost. The other issue I have noticed is that before, Memory Monitor would show App Memory as being one of the least in size & Cache the biggest but now that has completely reversed which is odd & I do not know why even if I only have Safari open. The numbers just do not add up & App memory is very big now. The system is definitely more memory hungry now - how do I correct this? Temps seem very stable averaging about 46-58 degrees doing basic stuff. Based on the above, does anyone think that the MBP has properly been able to reset things properly by itself & the computer is OK or am I living in borrowed time & this was just a sign of worse things to come? What happened here & is there anything I can do to stop this happening again? Sincere apologies for the long winded post but wanted to provide as much detail as I could remember. Many Thanks, Bazzy.