Send keys to Winamp

Try this. I've used WM_KEYDOWN instead.

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) 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_KEYDOWN = &H100

Private Sub Command1_Click()
    Dim hWinamp As Long
    'Get the hWnd of Winamp
    hWinamp = FindWindow("Winamp v1.x", vbNullString)
    'Send the X button to Winamp
    SendMessage hWinamp, WM_KEYDOWN, vbKeyX, 0
End Sub