This example tricks Windows 95 and Windows 98 into thinking that a screen saver is running - which also disables Ctrl+Alt+Delete and Alt+Tab. Note that this does NOT work on Windows NT!

Private Declare Function SystemParametersInfo Lib "user32" Alias "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam As Long, lpvParam As Any, ByVal fuWinIni As Long) As Long

Private Const SPI_SCREENSAVERRUNNING = 97

Private Sub Command1_Click()
  Dim ret As Integer
     Dim pOld As Boolean
     ret = SystemParametersInfo(SPI_SCREENSAVERRUNNING, True, pOld, 0)
End Sub

Private Sub Command2_Click()
Dim ret As Integer
     Dim pOld As Boolean
     ret = SystemParametersInfo(SPI_SCREENSAVERRUNNING, False, pOld, 0)
End Sub

Private Sub Form_Load()
Command1.Caption = "Disabled"
     Command2.Caption = "Enabled"
End Sub

Private Sub Form_Unload(Cancel As Integer)
'  re-enable Ctrl+Alt+Del and Alt+Tab before the program terminates
     Command2_Click
End Sub