I really understand how you feel, I live that everytime I fix my sister's PC...
Now when I pass a few minutes on a PC I go to the admin tools and disabled all the useless XP services (check the web for references on that) & install Spybot WITH TEATIMER tool enabled.
I also give a short class on Firefox and Thunderbird and warn the owner to never ever use Explorer or Outlook crap again.
Then I cross my finger that I wont get a "help me" call for at least the next month
