In Windows XP Service Pack 2, in the Security Center applet, there's a button that lets you set whether you would like to receive Automatic Updates. Its best to keep it in the default settong which is turned ON. To avoid a recurrence of spyware, install Spywareblaster. And get IE Spy-ad to lock down the Internet Explorer browser regardless of whether or not you use it. And of course, use Firefox or some other browser as much as possible to avoid IE's security flaws.
I'm going to have to print out this thread and think about buying a new computer. I still have Windows 98. I've been avoiding it because I'm not on the computer that much, and when I am, I usually only go to FR. I think I picked up spyware because I was researching weddings. (I had two daughters get married within the past year.)