OK first of all. Go here: http://www.safer-networking.org/index.php?page=download
Download the spyware remover and run it.
Then, go to: http://windowsupdate.microsoft.com/
and make sure you have all the critical updates installed.
Also EVERYONE that has Windows XP, enable the built-in firewall - instructions here: http://www.microsoft.com/windowsxp/pro/using/howto/networking/icf.asp