It doesn't default as an output. I tried this sketch:
void setup ()
{
digitalWrite (13, HIGH);
} // end of setup
void loop () {}
I must admit that pin 13 glows very faintly, but that is because the pull-up resistor has been enabled. You should add:
pinMode (13, OUTPUT);
... to setup to see it more clearly.
As for your problem, checking the pdf file about VirtualWire, he seems to be talking about a transmitter (TX-C1), a receiver (RX-B1) and a transceiver (DR3100).
Now you said:
I have bought a 433Mhz transmitter and receiver ...
Not the transceiver, right?
But you have in your code:
vw_set_ptt_inverted(true); // Required for DR3100
But you don't have that part.