I tell em that MS is dropping support after tax day next year for their beloved XP and the following tax-day, they'll be killing Windows Activation for all XP systems. In other words, you're now in the enviable position that your computer will not run after tax-day 2015.
Technically, that isn't accurate. you won't be able to activate XP, but Microsoft is supposed to be releasing a patch that will turn off activation. Even if they don't AntiWPA will take care of that problem. try googling for it. Granted almost every single antivirus program on the market tries to flag it, so you'd have to add it to the exceptions list.
Seems a reasonable bet... http://www.pcpro.co.uk/reviews/software/379933/avira-free-antivirus-13
I agree Avira is good, I've used it even way back on windows 95/98/98SE. The current versions do tend to spam you with pop-ups trying to get you to buy the full product, but even so only a couple of times a day. Not quite to the annoying enough to switch to something else stage, but still it is annoying. I totally recommend buying it just to support them, and help get rid of the pop ups. I used to recommend bitdefender when they allowed you to buy multiple year subscriptions, but not so much anymore.
The moon is a planet just like the Earth, only it is even deader.