Yikes! What an ordeal!

Hi. I've just gone through a messy ordeal with being hijacked, and the more I tried to fix, the worse it got. Finally, I had to restore my entire system, meaning I lost a lot of files I didn't want to lose

Now I'm trying to *prevent* this from happening again. I've installed Spywareguard and am using XP. My question is, there are four "accounts" on our XP OS, so how do I know that Spywareguard is running on all four when logged onto the internet? My teenage son goes to the music sharing areas (which I've told him not to do any longer) and his account is the one I'm most concerned with.

Thanks,
Karen