On some computers you can set what happens when you close your computer. On mine I can set it to turn off, go to sleep or do nothing. If you had the microphone recording and the computer was set to do nothing on closing, it should still keep recording. but the mic is going to be covered up and may not pick up much. You could plug in an external mic and have it laying in the direction you want to pick up. Now if you record your sister when her boyfriend is over she's really going to be mad. And recording someone with out their knowledge may be breaking the law where you are at, so be cautious.