capella playAlong is a program which among other things records music. For this music recording Windows Vista requests an installed recording device even though this device is not used by capella playAlong.
To solve the problem please simply connect a microphone, head phone or dummy connector to the pink microphone port of your computer. Now a window opens and you are asked which device you connected.
Please select "Microphone" (even though you might have connected something else). When you then address the area "Sound" on the control panel, you will find an installed microphone on the tab "Recording".