1   
2   procedure TForm1.FormCreate(Sender: TObject);
3   var
4     iHandle:Hwnd;
5   begin
6      Application.Title:='Temp'; //sets your application title to temp
7   
8   //looks for a pervious copy is running or not
9      iHandle:=Findwindow(pchar('TApplication'),pchar('One Copy'));
10    if iHandle>0 then begin // if found then display message
11  
12     messagedlg('You can only have one copy of this application running on a 
13  PC!'rror,[mbok],0);
14     application.Terminate; //terminates application
15  
16     exit;
17    end;
18  
19    //sets back to the current application title;
20    Application.Title:='One Copy';
21  end;
22