*** At module level, not included in any subroutine, I have the following:
***

Dim minuti As Integer
Dim secondi As Integer

Private Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long,
ByVal dwReserved As Long) As Long

*** The following is a subroutine that enables a Timer to work after having
pushed on Button1 placed on Form1, and set minuti equal to the content of
text1 textbox... ***

Private Sub Command1_Click()
minuti = Text1.Text
Timer1.Enabled = True
End Sub

*** ... and this is the timer that does a  count-down and *should* turn off
the PC  after having completed the count-down (minuti  < 0) ***

Private Sub Timer1_Timer()
If secondi = 0 Then
    minuti = minuti - 1
    secondi = 59
Else
    secondi = secondi - 1
End If

Text1.Text = minuti & "." & secondi

If minuti < 0 Then

' *** THIS IS THE CODE THAT *SHOULD* TURN OFF PC ***
Const EWX_SHUTDOWN = 1
Dim ResLon As Long
ResLon = ExitWindowsEx(EWX_SHUTDOWN, 0&)
' *** END TURN OFF CODE ***

End If

End Sub

---------------------------------------------
That's all. *Why this code is not correct?*
Important info:
1. This is the only code of this very simple program. In effect, this
program is composed by a module (the
Form1 one) and the code included in this module is the one given above and
nothing more;
2. I have tried to use this program on a Windows XP Home Edition operating
system and the problem is that the count-down is ok but when it arrives to
zero, it goes to -1 minuti and 59 secondi and *the computer is not turned
off*.

THANK YOU IN ADVANCE TO ALL THE ONES THAT WILL DECIDE TO HELP ME!

if it reboots or doesn't shutdown, you're outta luck here.  this shutdown
business is never consistent across machines...