I own a mid 2007 macbook that is become a royal pain. The computer can only reach temperatures of 80-85 Celsius before it totally shuts off. This occurs during CPU intensive activities such as watching movies, streaming video online, or running other CPU intensive programs. Online videos are pretty much unwatchable because the video will skip ahead and freeze while the audio continues to play. The stats are: OSX 10.6.X 2.16 ghz Core 2 duo 2 gb ram 120 gb hard drive (just reformatted) Cable internet Integrated video card About 2 years ago I had the same problem of the computer shutting off during high CPU usage on hot days in the summer. I took the computer to the apple store and they replaced my logic board under the warranty. I monitor fan speeds and temperatures using iStat pro and the fan is typically at 6200 rpm during video playback. I have had the issue with shutoffs in both Windows XP in bootcamp and in OSX I have explore lots of forums and tried all of the following: -used safari, firefox, and chrome -disabled adobe hardware acceleration (and enabled, neither works) -SMC fan control to force higher fan speeds I just erased the hard drive and have a clean install of Snow Leopard. Has anyone else had the problem of shut downs? I have used a 2009 unibody macbook and the temperatures during normal operation seem much lower that the 2007 macbook.