Option Explicit
Public Declare Function ReleaseCapture Lib "user32" () As Long
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Public Const WM_NCLBUTTONDOWN = &HA1
Public Const HTCAPTION = 2

Private Sub Image1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
    ReleaseCapture
    SendMessage Me.hwnd, WM_NCLBUTTONDOWN, HTCAPTION, 0&
End Sub