Electrostatic 3d simulator

hi everyone

I am looking for a electrostatic 3D simulator free or open source.
Basically I want to simulate the potential created in a particular place by some conductor with a fix voltage applied.

thanks!

You would like to have a look on this thread:
FREE electromagnetic simulators, rather than commercial ones

This one could do the job you want, I've used and it is very interesting:
http://www.femm.info/wiki/HomePage

thank you

I used femm but it is only 2D, i am looking for a 3D simulator

also I had a look on that thread, but I could not find one able to do electrostatic simulations. Femm would be perfect but it is only 2D