To close Winamp:

Code:
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As Any, ByVal lpWindowName As Any) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Const WM_CLOSE = &H10

Private Sub Command1_Click()

    'Get the handle of Winamp
    Retval = FindWindow(0&, "Winamp 2.5e")
    'Close Winamp
    SendMessage Retval, WM_CLOSE, 0&, 0&
    
End Sub