For Christmas '06, my wife and I gave our slightly older XP computer to my sister-in-law ( her single 36 yr old sister, that is).
It was fresh; I preloaded all the updates (like SP2) and installed and configured all the antivirus/antispyware etc - basically the system was out of the box plus up to date. Automatic updates, automatic scanning, shouldn't be any problems right?
Well, haha, jokes on me

. A few months later the system takes forever to start up, has one of those winantispyware2007 infections , multiple trojans/other virii.
After missing most of the MLB allstar game, since just to attempt to download single fixes it took on average 10-20 minutes, I got fed up and decided to do a total reformat. I thought this might also be a small wake up call to be more careful with her system as she lost tons of "important stuff" like pictures she got from the web, music, etc.
Twas not to be. Went over last night and it is the same story. Except this time she has managed to add in even more legit security programs, so aside from the nonstop winantispyware07 spam, there is almost nonstop AVG, McAfee, and some other programs "we blocked this and that" spam. Literally took me over 20 minutes to open one internet explorer window and get HJT downloaded to her machine.
So, after running HJT, I noticed that at some point she decided to reformat the damn thing again - how do I know? SP2 is not installed.

.I'm planning to do a total reformat again soon, which she agrees to.
What I need advice on, since this is something I've never had to do before, is how best to lock down the PC so this sort of destruction is not repeated as easily nor as often. This site needs a "tearing hair out" smiley.