Hi Justin,
Selecting "Pen Pressure" in the control menu does not mean it will "simulate" pen pressure. It means that you are choosing to control your brush size, angle, or roundness using your pen tablet. Obviously, if you don't have a pen tablet installed, that choice is not going to work for you :-) The only choice that will work for you (other than "Off") is "Fade". Select that choice and just use the sliders for your settings. If you try to use the Pen Pressure choice, Photoshop will put the warning icon up as a reminder that you don't have a pen tablet installed. Choosing "Fade" will remove that warning icon.
Here's a link to a good web page that explains a lot about the Shape Dynamics dialog.
http://www.photoshopessentials.com/basics/brushes/photoshop-brush-shape-dyn...
Hope this is helpful.
