I have a mid-2010 polycarbonate MacBook, and just upgraded the hard disk to 1 TB (HDD, not SSD; up from 250GB) and the RAM to 4 GB (up from 2 GB). Also, I replaced the bottom case using the MacBook Bottom Case Replacement Program by Apple (even though this is probably not related). Recently, however, I have witnessed my MacBook, on several occasions, just "freeze up" when more than 3 applications (not even graphics/processor/RAM intensive) are running. The applications would all work fine, and then suddenyl, everything would "freeze", the "spinning colored ball" would pop up and the computer would start to heat up. Usually, I would leave the computer along for about 15 mins., and when I return, the computer would be normal again. A few days ago, however, I noticed the fan running at extremely high speeds and making a lot of noise, and the computer's temperature rising. The screen also started to flicker for a short while and images were distorted. I would have to force shutdown my MacBook. This has been persisting for a few weeks. All my classmates, some of whom own MacBook Airs and MacBook Pros, do not seem to have the same problems, while those who own MacBooks say the problems they face with their computers are not as bad as the ones I do. Finally, when I am running software such as X-Plane 10 (and nothing else is running), my MacBook tends to display the symptoms I mentioned earlier. My friends with MacBook Pros and MacBook Airs (which are supposed to be not as powerful as even the regular MacBook) do not report the same issues. How can I solve these issues? Is there any reason why the polycarbonate MacBook in particular suffers from these issues? If so, could I upgrade my computer to MacBook Pro standard? Any help would be much appreciated.