Windows' multimedia architecture is based on DirectShow, which works basically as a collections of filters with input(s) and/or output(s) for data. Every multimedia component is represented by a DirectShow filter. This includes audio/video compressors/de-compressors, but also the input/output of your soundcard, along with many others. By connecting filters together, you create?data paths for multimedia data, eventually resulting in an action (for example a video compression conversion).
Microsoft's DirectShow SDK (Software Development Kit) comes with a great application called Graph Edit, which allows you to graphically build filter graphs, thus manipulate directly every multimedia component of your system!