Ultimate Pack  hot! Image Editor  new! Runtime Fusion Form Designer Object Inspector Print Suite Pro Commented Image Delphi Toys WinDowse Delphi Bonus TMS Scripter Studio Form Designer VB Form Designer .NET ...get more... for Delphi.NET, C#, VB.NET for Delphi VCL, BCB 3-6

	WinAPI Online Unix Manual Pages MegaDetailed.NET in3steps.com cdtrrracks.com new!   greatis.blogspot.com

You should set your own procedure to OnIdle event of application. Use GetAsyncKeyState function in it.

type
  TForm1 = class(TForm)
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
  private
    procedure PrintScreenDetect(Sender: TObject; var Result: Boolean);
  public
  end;
...
procedure TForm1.FormCreate(Sender: TObject);
begin
  Application.OnIdle:=PrintScreenDetect;
end;

procedure TForm1.PrintScreenDetect(Sender: TObject; var Result: Boolean);
begin
  if GetAsyncKeyState(VK_SNAPSHOT)<>0 then
    Label1.Caption:='PrintScreen Key was pressed';
  Result:=True;
end;

For more

Delphi Help

Download source