If you are experiencing a problem where the monitor just goes black or freezes up without any kind of error message while running ShowSim, and this problem never happens when using any other program, then the most likely cause is that your graphics card is overheating.  High-end graphics cards will add a substantial amount of heat into your system while using ShowSim that isn’t generated while using most other applications (with the exception of games). 

If the internal temperature of your computer rises much above 100’ F then you can experience the screen blacking out or freezing up when the graphics card overheats, forcing you to reboot your computer by yanking the power cord as the only way to reset it.  In a computer that is designed for gaming you should already have the required cooling system for running larger graphics cards, but if you are retrofitting an existing PC with a larger graphics card then this is an issue that you will have to look at.  A typical system for running fast graphics cards will have at least three 120mm fans installed: one in front, one in back and one in the side or sometimes one on top.  An older PC with a single fan in the back just isn’t going to work and you will overheat the card.  It is not usually very easy to modify an existing PC case to add additional cooling fans, so it is  better to just buy a PC that has already been configured with the proper cooling system to begin with. 

Some systems also give the option of having a temperature monitoring panel installed on the front, which shows you a graphic display of temperature readings taken at various locations inside the computer.  These don’t really cost that much extra and are useful for troubleshooting temperature problems inside your computer.  When fans eventually fail, and they all do, you often will not notice that it has stopped spinning.  Dust accumulating in the intake vents is another problem that occurs over time, and can reduce the airflow to the point of causing heat problems.   Having a temperature readout panel will alert you to these problems so that you can replace the fan or clean out all the dust before your computer starts crashing.

So if you are experiencing this problem, take the following steps:

1) Make sure your computer has at least three 120mm fans for the cooling system.

2) Make sure all fans are running, as they only last a few years before the bearings wear out.

3) Make sure there is not an excessive amount of dust blocking the air vents.  A layer of dust can also build up on the graphics card itself, trapping heat or causing shorts.  The amount of dust that can build up over a five year time period can be substantial and will choke off the airflow in your computer.  The best solution to the dust problem is to open your case and blow it out with an air comprerssor (be sure to do this outside, as it will create a large dust cloud!).