Hello Colin,
[...] then it shuts down (doesn't shut the PC down though).
This is commonly referred to as a "crash to desktop" (abbreviated: CTD), and happens to many simmers. Flight Simulator is a very modifiable game -- that's both a blessing and a curse. Much as the variety of possible modifications and add-ons available, there is also a variety of issues that cause CTD. To find the cause, you usually need to narrow things down.
I run it for about an hour then it shuts down (doesn't shut the PC down though).
Do you regularly experience CTDs after a certain amount of playing time? (Like "the last six times is played FS, it always crashed after 50-70 minutes.") Does this happen with a certain aircraft or in a certain region, or does it happen with any aircraft, anywhere? Do you use any add-ons? They can cause problems if they are not installed correctly.
I can run other programs for a lot longer with no problems. I have been monitoring the CPU temp but its not going above the norm either.
It might also be a hardware problem. The easiest way to check this is running a hardware-demanding 3D-game and see if it also causes trouble or crashes. Then, there are test programs. A good program to check the CPU is Prime95 (can be run from Windows;
Homepage; the short
Wikipedia article is a good introduction). Checking the RAM can be done with Memtest86+ (you need to boot it from a floppy disk, CD or USB device;
Homepage;
Wikipedia).
Another "root of evil" are driver problems. I experienced similar trouble myself recently, maybe reading this helps you, or you recognize similar symptoms. I had trouble with my video driver (AGP/Radeon 9800 Pro), all the ATI tabs were gone in Windows' advanced display settings. I installed the Omega Drivers from
omegadrivers.net, and the ATI settings tabs were back, but now games don't recognize my video card's advanced features. All graphics are now calculated by my GPU without any hardware acceleration, which results in a noticeable frame rate drop. I use Asus PC Probe (which shipped with my MB) for monitoring and when playing FS2004 or CivIV, it frequently displays small drops of the +3.3V voltage, which supplies the video card. These games used to run stable (as did my PC), but now they often crash after one or two hours of playing. (I'm still working on this issue.)
That's it for now. Hope we figure out your problem.