Защита приложения от выключения через ctrl+alt+del

Private Declare Function SystemParametersInfo Lib 
"user32" Alias "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam As Long, ByVal lpvParam As Any, ByVal fuWinIni As Long) As Long
 
Sub DisableCtrlAltDelete(bDisabled As Boolean)
 
Dim X As Long
 
X = SystemParametersInfo(97, bDisabled, CStr(1), 0)
 
End Sub
 
'Usage:
 
'To disable Ctrl-Alt-Delete:
 
Call DisableCtrlAltDelete(True)
 
'To enable Ctrl-Alt-Delete:
 
Call DisableCtrlAltDelete(False)
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Вот ещё пример, как заблокировать крестик (X)  и др. на форме
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Option Explicit
 
Private Declare Function DeleteMenu Lib "user32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long
Private Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
 
Private Const MF_BYPOSITION = &H400&
 
Private ReadyToClose As Boolean
Private Sub RemoveMenus(frm As Form, _
    remove_restore As Boolean, _
    remove_move As Boolean, _
    remove_size As Boolean, _
    remove_minimize As Boolean, _
    remove_maximize As Boolean, _
    remove_seperator As Boolean, _
    remove_close As Boolean)
Dim hMenu As Long
    
    ' Get the form's system menu handle.
    hMenu = GetSystemMenu(hwnd, False)
    
    If remove_close Then DeleteMenu hMenu, 6, MF_BYPOSITION
    If remove_seperator Then DeleteMenu hMenu, 5, MF_BYPOSITION
    If remove_maximize Then DeleteMenu hMenu, 4, MF_BYPOSITION
    If remove_minimize Then DeleteMenu hMenu, 3, MF_BYPOSITION
    If remove_size Then DeleteMenu hMenu, 2, MF_BYPOSITION
    If remove_move Then DeleteMenu hMenu, 1, MF_BYPOSITION
    If remove_restore Then DeleteMenu hMenu, 0, MF_BYPOSITION
End Sub
 
Private Sub cmdClose_Click()
    ReadyToClose = True
    Unload Me
End Sub
 
Private Sub Form_Load()
    ' Remove the Close system menu item and the
    ' menu separator.
    RemoveMenus Me, False, False, _
        False, False, False, True, True
End Sub
 
' Cancel if ReadyToClose is false.
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    Cancel = Not ReadyToClose
End Sub