Disable the Standard Window Close (X) Button

Private Const SC_CLOSE As Integer = &HF060
Private Const MF_GRAYED As Integer = &H1
 
Private Declare Function GetSystemMenu Lib "user32" 
(ByVal hwnd As Long, ByVal bRevert As Long) As Long

Private Declare Function EnableMenuItem Lib "user32" 
(ByVal hMenu As Long, ByVal wIDEnableItem As Long, ByVal wEnable As Long) As Long  

Private  Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs)
   EnableMenuItem(GetSystemMenu(Me.Handle, False), SC_CLOSE, MF_GRAYED)
End Sub