Code:

uses

Registry;

{....}

procedure TForm1.Button1Click(Sender: TObject);

var

Reg: TRegistry;

KeyName: string;

ValueStr: string;

begin

Reg := TRegistry.Create;

try

   Reg.RootKey := HKEY_CLASSES_ROOT;

   KeyName  := 'htmlfile\shell\open\command';

   if Reg.OpenKey(KeyName, False) then

   begin

     ValueStr := Reg.ReadString('');

     Reg.CloseKey;

     Label1.Caption := ValueStr;

   end

   else

     ShowMessage('No Default Webbrowser !');

finally

   Reg.Free;

end;

end;