Control Panel\All Control Panel Items\Power Options\Edit Plan Settings\turn off the display:
Make sure that you are adjusting the power management plan that is active.
If that's set correctly and you are still having problems, check the settings for the screen saver. Failing that, reset the Power plan options to default and reconfigure to your preferences. Alternatively, create a new power pan and make it active.
You may have to do this with an administrative account.
SD