Smartclose is very good (similar to GameBooster) and is also free.

Even though there is an 'installation wizard', it is self-contained and portable, and had no probs running off usb on many diff computers, directly from it's install folder.

Is very good, and IMO way better than game booster pro, and I use it often when I feel my PC getting sluggish or right before gaming. Program is found all over net, e.g. on CNet.

Publisher's page: http://bmproductions.fixnum.org/smartclose/index.htm
Compatible with all ver of Windows.
Publisher's Description: "SmartClose is a free program that automates the process of closing all running programs. It can also save the state of the system to a system snapshot, so all the programs that have been closed can be easily restarted later by SmartClose."