might answer a few more questions for you; from there (if you have a clearer picture of what you want), go to the various manufacturer websites and see what they have to offer.
http://www.ghowto.com/technology/how-to-choose-a-computer.html

As for PC security programs; there are alot to choose from, anything from the most basic to programs for intermediate PC users. It depends whether or not you trust using free programs or would rather spend money for a program.