Game Booster 2.0 Free http://www.iobit.com/gamebooster.html is a great program designed for gamers, at the click of a button it will disable any un-necessary programs from using valuable resources that could go towards games, thus boosting performance. I've been using it for a long time and its great.

Also, Avira AntiVir Free http://www.avira.com/en/avira-free-antivirus is a great antivirus that Gizmo's Freeware http://www.techsupportalert.com/ has named the best freeware antivirus program. I also have been using this for a long time and its great.

they are not portable ...