AVG is a well recognised anti virus and anti spyware program, with the added benefit that it's free.....
Also you may want to check out this website for other free ones which are even better and there is everything from free industry standard firewalls to backup software to the latest anti virus/spyware. Read some of the reviews on the website and I doubt that you will be dissapointed. I use it and quite frankly I find it better than anything else that I have used and for the record I would'nt touch McAfee or Norton for that matter with a 50ft barge pole!!!!!!!!!.
www.comodo.com.