I am not entirely sure what your use of the software is, but there is an electonics/electrical program by the name of PSPICE that has a free demo with all working features available for download or you can request a CD. Its more geared toward the electronics industry, but I have been told there are electrical downloads for it. Below is the link to the site.
http://www.orcad.com/Product/Simulation/PSpice/eval.asp
