There are other API's for playing sounds from files.
>Where do i find these functions and to call them ?
They are documented in MSDN. Sadly MSDN is normal microsoft quality so you usually have to read some tutorials on the web to figure out exactly how to use them.
> Do i have to find the Datasheets to the sound card chips?
You don't. You apply your sound modifications to your data buffer the chip will be mixing in with (possibly) other data buffers into a final output buffer that is output to speaker or whatever is hooked up to the output line of the card. You canalso give instructions to the OS to change some parameters like data size (8 or 16 or 24? bit), panning, volume, buffer size, sampling rate, stereo/mono etc, and you can also set up an FX chain (flanging, phase, reverb etc.) You do this in DirectSound, part of the DirectX package. Download the DirectX sdk and get to work.