SPICE
SPICE is a simulation program developed to simulate electrical circuits. SPICE can also be used to solve economic and financial problems. More information about SPICE can be found at the two links below:http://en.wikipedia.org/wiki/SPICE
http://bwrc.eecs.berkeley.edu/classes/IcBook/SPICE
The LT-SPICE program is free and can be downloaded to your Windows computer.
LT-SPICE has a schematic editor
LT-SPICE has the SPICE simulator
LT-SPICE has an integrated graphical display of the simulation results
The LT-SPICE Circuit Simulator Video: