When you say that the service is not working, does it mean that you are unable to start the service or that the UPS options cannot be configured in the Power Options? I've seen some stubborn cases where after SP2, the OS insists on treating the COM-connected APC UPS as a serial mouse. Check if the service is running properly, restart if necessary, check the serial connections and the serial port hardware properties. In my friend's case, unplugging the UPS, stopping the service, restarting the PC and then plugging the cable back in and restarting the service fixed the problem.
