uses ShellAPI;
 // ..
 class
   TAboutBox = class(TForm)
     // ..
     URLLabel : TLabel;
   end;
 // ..
 
  URLLabel.Cursor := crAppStart; { set this in the object inspector }
 // ..
 
 // onClick event handler
 procedure TAboutBox.URLLabelClick(Sender: TObject);
 var TempString : array[0..79] of char;
 begin
   StrPCopy(TempString,URLLabel.Caption);
   ShellExecute(0, Nil, TempString, Nil, Nil, SW_NORMAL);
 end;