Volvo revised the S40 midway through the 2004 model year, and for 2007, there were only a handful of small changes. The 2007 changes included standard stability control and a package that added an MP3 player input and a body kit. Also included on the 2007 S40 was a service reminder system that illuminated a "Service" light on the instrument cluster when it was time for an oil change.
Press and hold the tripmeter reset button, then turn the S40's ignition to the "II" position. Continue to hold the tripmeter reset button until the "Service" light starts flashing -- about 30 seconds. Release the tripmeter reset button, listen for the audible ding, then turn the ignition off. Turn the ignition back to the "II" position and check that the "Service" light remains off. If the light turns back on, then turn the ignition off and restart the procedure.
