Keep a watch on this site daily . You'll definitely find something useful:
http://www.giveawayoftheday.com
They give out paid apps free each day , legally(that's the best part).
Sometimes useful apps too
Avast/Avg especially since it's a fresh and ready to be exploited windows xp :lol:
you should just install as many viruses as you can and see if you can successfully clean it. just for fun.