I recently bought used Mid 2009 MacBook Pro 17 inch model with 2,8 GHz Intel Core 2 Duo Penryn T9600 processor, 8 GB of RAM, and two NVIDIA GPUs - 9400m (integrated) and 9600m GT (discrete). It seemed like quite a bargain considering it did cost me an equivalent of $240. Of course such cheaply sold machine had to have some issues - in this particular case the seller reported problems with 9600m GT chip, which caused the MacBook Pro to randomly restart. Such problem reportedly occurred mostly when the charger was plugged into the Magsafe port which triggered a switch to the discrete graphics. Considering I didn't intend to use the machine to perform GPU-intensive operations, I figured I'd just switch off the 9600m GT and that should solve the problem. First, I replaced the original HDD with new SSD. Although I've prepared a bootable USB with El Capitan on my MacBook Air, somehow I couldn't boot with it, so I went ahead with installing Windows 7 instead (highest Windows version on this machine supported by Apple). It was running pretty smoothly, however the problem was, of which I wasn't previously aware, that MacBook Pro arbitrarily disables integrated GPU when running Windows if a particular model shipped also with a discrete GPU. Therefore, I couldn't really execute my original plan. Since I suspected that this whole issue with 9600m GT was heat related, I resorted to aggressively cooling the MacBook Pro with the fans - I set them to reach maximum speed of 5700 rpm as soon as the temperature at GPU diode reaches 75 degrees Celsius. The fans were successful in keeping the temperature below that point, while CPU diode reading sometimes exceeded 80 degrees C - still normally a rather benign condition. Despite this, the computer randomly went into blue screen, saved crash dump and restated - sometimes after several minutes, and sometimes after over half an hour of uptime. I started to have some doubts whether it really was the excessive-heat-related issue. The temperature readings weren't all that bad at the time of the crash, although after a restart the fans were back at full speed which indicated that the temperature threshold was somehow exceeded, and the whole computer case felt quite hot, but - well - that's what you may expect from aluminum unibody notebook. Then I did a hardware check and found out that the RAM installed in this MBP is actually a 1333 MHz DDR3 memory. I've read that this model supports only 1066 MHz RAM. Apparently the previous owner upgraded the memory in the computer, but overlooked possible compatibility issues. What's more, I found out that this RAM is currently severely underclocked, running at only 666 MHz. So do you think that RAM is the real answer, and buying 1066 MHz sticks could resolve issues with this MacBook Pro? Or is it just running at half its potential speed and that's it, no problem? What other options of resolving the problem might I have? I guess I could try disassembling it once again to blow some compressed air into the fans and possibly also replace thermal paste. No other solution comes to my mind, well, except for just selling it - I've seen many exact same MacBook Pro models on sale with similar price that couldn't even boot PS As I was writing this post, El Capitan was installing itself on the aforementioned MBP after finally succeeding in making bootable install USB. Sadly, it crashed before the installation was done.