First we have to recognize you will be using a 64bit operating system, which will require 64bit compatible applications.
Consequently we need to look for 64bit antivirus firewall solutions, a simple search in google will probably bring up a few, remember to add 64bit in your query. A point to remember most 32 bit applications will work but you may experience performance issues which may affect you taking advantage of your 64bit OS.
Personally I recommend AVG free or Avast, they are pretty good and cover most bases. AVG is quite easy to set up and configure. However it doesn't offer much intererms of firewall protection where the free version is concerned. So your best bet is AVAST it fully comprehensive. It has root kit protection, anti virus protection and of course firewall/network protection which has some anti spyware protection features. I also recommend installing Windows defender for additional security just remember do a little configuration after installation. The plain vanilla installation just isn't good enough security.
Hope this helps.
Earle Ramage