I can't change the mouse for left-handed people use the computer.

You need to install xorg-xmodmap package to configure the mouse buttons.

Install xorg-xmodmap package. In a terminal, type:

# tazpkg -gi xorg-xmodmap

To configure the mouse for left-handed:

# xmodmap -e "pointer = 3 2 1"

To configure the mouse for right-handed:

# xmodmap -e "pointer = 1 2 3"

To check what is the configuration of your mouse, type:

# xmodmap -pp

Reference: http://forum.slitaz.org/topic/mouse-left-handed