R is a fully comprehensive statistical program that can be run on any platform. Download it for free here: R-project. There is a large community of R users and resources freely available. Below, I have posted links that I have found to be very helpful.
I also recommend the use of a good script editor, my favorite being Tinn-R. To run the parentage programs on this website you only need to learn how to do two things (1) successfully import data - where most problems arise from incorrectly setting the working directory or having an improperly formatted input file and (2) copy and paste script into R (which is where I find Tinn-R to be most useful). Please contact me if you have any difficulties with these programs and I will do my best to help.
R-card - A 3 page pdf with basic R syntax.
Ecological models and data in R - A useful introduction with helpful labs.
OSU R group - An Oregon State University, graduate-student run site - lots of helpful script files.
R for beginners - a useful pdf!