Notebooks won’t turn off

Hi,
I have a client who has a new (4 months) MSI M510C notebook, with XP2 home, which will not turn off. He has disabled all power settings, including hibernate, and standby.
When he turns the computer off it does the “right thing” but after a while when he returns to the computer there is a screen saver running. The only way he can turn it off is to remove the batteries.
The computer is stand alone, with dial up internet access.

Incidently, his wife’s work supplied HP (unknown model) does the same. She solves her problem by sticking it into her cupboard at work and locking the door.