How to temporary disable the sound card, or at least microphone function without unplugging the microphone?

The specific method of muting your microphone is dependent on the sound card you're using. You can try going into the control panel and opening the 'sound and audio device' window and deselect, or mute the microphone the microphone, or if you have the speaker icon on your task bar, open that up and see if you have the option of muting the microphone.