surface potential calculations

I would like to perform calculations of the surface potential of various
 proteins (pdb files available). I know that such things were previously
 carried out using Delphi. How can I do these calculations if Delphi is not
 available to me?
 Thank you for your assistance,
 Tal Peleg-Shulman.
 Tal Peleg-Shulman				talp' at \`
 Dept. of Pharmaceutical Chemistry		phone: 972-2-6757543
 School of Pharmacy, P.O.B. 12065		fax: 972-2-6410740
 The Hebrew University of Jerusalem
 Jerusalem 91120