J'étais à la recherche d'une methode pour arreter, mettre en veille ou redémarrer Windows Vista.
Voici le résultat
Arreter le programme

        System.Diagnostics.Process.Start("shutdown", "-s -f -t 100") 'Shutdown
    
Mettre en veille

        System.Diagnostics.Process.Start("shutdown", "-l -f -t 100") 'Logoff
    
Redemarrer

        System.Diagnostics.Process.Start("shutdown", "-r -f -t 100") ' Restart

type
  TSystemShutdownType = (sstCloseSession, sstPowerOff, sstReboot, sstShutdown);
function SystemShutdown(const ShutdownType: TSystemShutdownType= sstPowerOff): Boolean;
var
 TokHandle : THandle;
 TokPrivilege: TTokenPrivileges;
 ReturnLength, SizeOfTokPrivilege : Cardinal;
begin
  Result := OpenProcessToken(GetCurrentProcess, TOKEN_ADJUST_PRIVILEGES, TokHandle);
  if not result then
    exit;
  try
    SizeOfTokPrivilege := SizeOf(TokPrivilege);
    FillChar(TokPrivilege, SizeOfTokPrivilege, 0);
    ReturnLength := 0;
    TokPrivilege.PrivilegeCount := 1;
    LookupPrivilegeValue(nil, 'SeShutdownPrivilege', TokPrivilege.Privileges[0].Luid);
    TokPrivilege.Privileges[0].Attributes := SE_PRIVILEGE_ENABLED;
    AdjustTokenPrivileges(TokHandle, False, TokPrivilege, SizeOfTokPrivilege, nil, ReturnLength);
    if GetLastError <> ERROR_SUCCESS then
      exit;
    case ShutDownType of
      sstCloseSession : result := ExitWindowsEx(EWX_LOGOFF, 0);
      sstPowerOff     : result := ExitWindowsEx(EWX_POWEROFF, 0);
      sstReboot       : result := ExitWindowsEx(EWX_REBOOT, 0);
      sstShutdown     : result := ExitWindowsEx(EWX_SHUTDOWN, 0);
    end;
  finally
   CloseHandle(TokHandle);
  end;
end;

Public Sub ElgWMIRemoteBoot(ByVal Machine As String, ByVal Login As String, ByVal MotDePasse As String, ByVal Action As Integer) 
Try
Dim co As New ConnectionOptions 
If (Not Login.Trim.Length = 0) Then

co.Username = Login

If (Not MotDePasse.Trim.Length = 0) Then

co.Password = MotDePasse

End If

End If

co.EnablePrivileges = True

co.Impersonation = ImpersonationLevel.Impersonate
Dim aManagementScope As New System.Management.ManagementScope(String.Format("\\{0}\root\CIMV2", Machine), co) 
Dim aObjectQuery As New System.Management.ObjectQuery("SELECT * FROM Win32_OperatingSystem")
Dim aManagementObjectSearcher As New ManagementObjectSearcher(aManagementScope, aObjectQuery) 
Dim aManagementObjectCollection As ManagementObjectCollection = aManagementObjectSearcher.Get()
For Each aManagementObject As ManagementObject In aManagementObjectCollection 
Dim ParamObject(1) As String
Select Case Action 
Case 0 : ParamObject(0) = "4" ' Ferme session

Case 1 : ParamObject(0) = "6" ' Redemarre

Case 2 : ParamObject(0) = "12" ' Eteind

End Select
aManagementObject.InvokeMethod("Win32Shutdown", ParamObject) 
Next
Catch ex As Exception 
MessageBox.Show(ex.Message, "Erreur", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try


End Sub