SystemParametersInfo(SPI_SCREENSAVERRUNNING,1,NULL,0);//使CTRL ALT DEL Alt Tab 開始鍵功能失效

Question:
How can I globally trap the Windows system key "PrintScreen"?    Answer:
The following example demonstrates registering a hot key 
with the
system to globally trap the windows printscreen key.    Example:        type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    procedure WMHotKey(var Msg : TWMHotKey); message WM_HOTKEY;
  public
    { Public declarations }
  end;
   
var
  Form1: TForm1;
   
implementation
   
{$R *.DFM}
   
const id_SnapShot = 101;
   
procedure TForm1.WMHotKey (var Msg : TWMHotKey);
begin
  if Msg.HotKey = id_SnapShot then
    ShowMessage('GotIt');
end;
   
procedure TForm1.FormCreate(Sender: TObject);
begin
  RegisterHotKey(Form1.Handle,
                 id_SnapShot,
                 0,
                 VK_SNAPSHOT);
end;
   
procedure TForm1.FormDestroy(Sender: TObject);
begin
  UnRegisterHotKey (Form1.Handle, id_SnapShot);
end;