Travar as teclas: Alt+Tab, Ctrl+Esc, Ctrl+Alt+Del

var OldValue : LongBool;

begin

  SystemParametersInfo(97, Word(True), @OldValue, 0);

end;

Destravar as teclas: Alt+Tab, Ctrl+Esc, Ctrl+Alt+Del

var OldValue : LongBool;

begin

  SystemParametersInfo(97, Word(False), @OldValue, 0);

end;