Using the command line interface to control Winamp
 
The simplest, easiest, least powerful way of controlling Winamp is to execute winamp.exe yourself. By simply calling winamp.exe with various command line options, you do a number of things. For example:
 
C:\path\to\winamp\winamp.exe /ADD C:\mp3\whatever.mp3
(Adds C:\mp3\whatever.mp3 to the playlist of a running Winamp, if Winamp is running, otherwise it opens Winamp and plays it outright)
 
C:\path\to\winamp\winamp.exe /NEW
(Creates a new instance of Winamp, even if Winamp is already running)
 
C:\path\to\winamp\winamp.exe C:\mp3\file.mp3
(Plays the file C:\mp3\file.mp3, regardless of whether or not Winamp is open)
 
C:\path\to\winamp\winamp.exe /CLASS="myclassname"
(Opens Winamp with a different Window Class name "myclassname" )  
As you might notice, what you can actually do using the command line interface is pretty limited. It is really easy to get started with, though. You can also specify multiple files and or directories on the command line, such as:  
C:\path\to\winamp\winamp.exe /NEW "C:\my mp3s\" "C:\bigplaylist.pls" "C:\download\new song.mp3"

we'll assume some basic knowledge of 32 bit Windows programming