Tonecache is a small, completely free program that lets the user capture any sound that comes out of the speakers, and save it as a WAV file.
Tonecache is designed to capture these sounds, without you having to worry about filenames or overwriting, so that you can focus on the capture, not on their administration (which is automatic: the program gives the files their names).
Tonecache also includes a volume control for you to choose the sound power of the recording.