"%ProgramFiles%\Winamp\winamp.exe" "%AppData%\Winamp\Winamp.m3u"
If your Winamp isn't set for multiuser usage and previous code doesn't work try to change it to:
"%ProgramFiles%\Winamp\winamp.exe" Winamp.m3u
This code will start Winamp and set them to play last played playlist. In first code last played playlist is in your Application Data folder (if Winamp is instaled in multiuser mode). In Second winamp.m3u file is located in Winamp installed folder.
If your Winamp isn't installed in your Program Files folder, you need to change first part of command: "%ProgramFiles%\Winamp\winamp.exe" to full path to your winamp folder.
