Volvo 2008 S40 Owner's Manual page 64

The electrically operated rear door windows can be disabled by a switch located on the driver's door (see illustration).
If the light in the switch is OFF: The rear door windows can be raised or lowered with the buttons on the rear door
armrests or with the buttons on the driver's door armrest.
If the light in the switch is ON: The rear door windows can only be raised or lowered with the buttons on the driver's
door.
Power window control - front passenger's side
The control for the power window in the front passenger's door operates that window only.
Power windows in the rear doors
The rear door windows can be operated with the control on each door and with the switch on the driver's door.