One bad work station?

HELP!!!!!
Server is running win 2000 server. I have 20 work stations. One station logs off with no rime or reason?
I have replaced all hardware. New wire to switch. changed ports. setup new account for user. Station does not loose internet connection. So no bad wiring? is there any software (i can afford) to log workstation active? Also have to power down to log back on? Has to be a software issue.
This user has every program known to man.
thanks
Frank