If you have never done that before programming sound card at the IO level will be hard. I would look for sound libraries or OS API. A lot depends on what you plan to do.
Thanks, My OS is windows xp 32bit. actually I need a prepared C library which can be used in lcc-win32. My project is quite simple; It should receive in each instant the intensity of an external sound from mic, doing some quick processess, and after that send an calculated intensity to speaker immediately.