Audio Capture / Recording Live

We want to develop an application that can record "What-U-Hear" creative like, which means ALL sound played and sent to speakers... To assign you the product we want you to briefly explain us how you plan to programatically ? record all audio that's being played back on any type and brand of? sound card ? In C++ or delphi or C# (I mean, like recording ALL that is played on windows/speakers...)