2007 S40 Battery Issue

[soul2tha]

I had a few things randomly happen at the same time and now I'm having an issue with my battery. My passenger door stopped working (lock, window, etc.) about 2 weeks ago. Yesterday I went to start the car and the battery was dead and at the same time the "Alarm Service Required" warning came on. When I went to get the battery tested and replaced, the tester that they used said "Signal Noise" and it wouldn't test the battery. Could something be running constantly that's draining the battery, and if so, what? I took out the fuse to the alarm as well. Any input would be appreciated!