OS: CentOS 5.4

1. Add following line into $HOME/.Xmodmap: add control = Super_L
2. Add following line into $HOME/.xinitrc: usr/bin/xmodmap $HOME.Xmodmap

check xmodmap manual for more information.

OS: Ubuntu 10.x

1. Go into System -> Preferences -> Keyboard
2. Click on the “Layouts” tab and then click the “Layout Options” button.
3. Click on “Alt/Win key behavior”
4. Select “Control is mapped to Win keys (and the usual ctrl key).