Hi, I purchased a brand new Macbook Pro mid 2010 15" (i7, 4 gigs, 512 gigs) in early 2011. That was my first Mac and I was more than happy with it. It had Snow Leopard back then and it was working flawlessly, very fast and it never crashes. Some years later, I had to upgrade it to Mountain Lion as the new XCode release didn't support Snow Leopard anymore. My Mac was then way slower and not as stable. I researched the Internet and did some actions to improve it (like resetting the PRAM). It was slower than with Snow Leopard but it was still working fine with no crashes. Than came Mavericks. I upgraded and I found my Mac to be more responsive, faster and was happy with this OS for many years. So much that I didn't upgrade to Yosemite or El Capitan. Fast forward in time to a few months ago (like September/October 2016). Before then, with Mavericks, my Mac was still working perfectly, it never crashes. But since that time, it began to crash once in a while... but now, it crashes at least once a day... for no reason. I didn't install anything new (still Mavericks), I didn't change any hardware and it seems to crash randomly. In other words, I'm not doing anything special, just browsing the web with Firefox/Chrome, I sometimes use OpenOffice, sometimes iTunes, but that's it, no games, no complicated softwares. When It crashes, the screen turns black for a few seconds, then gray with a message to reboot, I press any key and it reboots. This is obviously very annoying... but I don't want to buy a new Macbook Pro as they are now quite expensive and performance wise, I am still satisfied with my mid 2010. Here's what I tried: - I upgraded to macOS Sierra. - I upgraded the RAM from the original 4 gigs to 8 gigs (bought a reliable brand on Amazon). - I reset the PRAM. I then did some researches on the Internet and found many posts saying that it might have to do with the video card. I remember a long time ago that some Macbook Pro mid 2010 had some issues with it. Back then I ran the diagnostic tool and everything was fine. And since my Mac was working perfectly, I didn't bother more with it. I then tried this: - Disabled the "Automatic graphics switching" in the "Energy Saver" options. - Installed the gfxCardStatus application. I tried many different releases. I tried forcing it to "Integrated Only" but couldn't since I'm using an external monitor. I tried forcing it to "Discrete Only". - Disabled the "Use hardware acceleration when available" setting of some applications (Firefox and Chrome). But even after all this, I still have the same problems, it's not even better, it still crashes a least once a day. So now, I'm kind of confused. Is my problem really with the video card? If so, I read that I might need to change the whole motherboard... and I assume Apple won't do that for free since my Mac is out of warranty. Why did I start having problems just a few months ago? Or it might not be related to the video card at all. Either way, I don't know what to try anymore. Any suggestions? Thanks a lot!