Nombre de la PC remota

[delphi.com.ar]

Prueba esto:

Código Delphi [-]
uses
  WinSock;

function GetHostNameByIP(IPAddress: string): string;
var
  WSAData: TWSAData;
  HostInfo: PHostEnt;
  ulIP: Integer;
  pIP: PChar;
begin
  Win32Check(WSAStartup($0101, WSAData)=0);
  try
    ulIP := Inet_Addr(PChar(IPAddress));
    pIP  := PChar(@ulIP);
    HostInfo := GetHostByAddr(pIP, 4, AF_INET);

    if Assigned(HostInfo) then
      Result := HostInfo.h_name
    else
      Result := '';
  finally
    WSACleanup();
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(GetHostNameByIP('136.1.240.21'));
end;

Saludos!