I would like to run Git 1.6.x for Windows from a USB memory stick.
There is a Windows version of Git available at: http://code.google.com/p/msysgit/
Installing a
Your e-mail address, name and many other settings are stored in the global configuration file .gitconfig in your home dir.
git-config
Maybe the -f option helps you for specifing the different location of the config file.