Gajadur, There is /etc/default/halt (or so, i'm no more using Debian), you can try to switch to the alternative. Maybe it works... If not, try to find out which command (as root or via sudo, from a terminal) does shut down the machine. For example, "shutdown -h now" should never do a reboot. If that command works, put it into a xfce4 panel button and use that instead of 'logout'. Or just hack the logout button. hth