I just faced the issue on an 03 S60, which has a servce message box rather than a light. In any case I called Volvo North America and they, somewhat hesitently, told me how to do it. Yours may or may not be the same. Their number is 800-458-1552. On my car you turn the key to ignition position 1, push and hold down the odometer button while turning the ignition to position 2. After a few seconds the hazard light will start flashing at which point you can release the odometer button. It should then be reset. Again yours may be different but Volvo NA should know. They guy I talked to looked it up in book. It's completely obscene that a dealer would try to charge for this.