I once tried out Battlefield Heroes which installed Punkbuster along with it. I'd think it's about the same but didn't hide like a rootkit. After completely removing the game Punkbuster still ran in my memory while I had no game that used it! It most certainly did not offer to remove it along with the game and had I not checked manually I would never have known it was still there. I get a bit offended when games fail to remove useless programs taking up system resources no matter how small. If Punkbuster did this I'd not assume Game-guard is different, I'd make sure.