It looks like http://arduino.cc/forum/index.php?topic=111.0
is the new location of the tutorial. I tried to edit the page to correct that, but don't have privileges and can't find contact details for any of the previous editors (Scott Fitzgerald / Federico).
From the schematic for the USB2Serial Light, HWB comes out on pin 6 of the flat header opposite the USB, so can be connected to pin 1 on the same header to pull it down into reprogramming mode.
In my case even after going through a reset with HWB pulled down, the board still reports as VID 0000 and PID 0000 so I guess it is faulty, but hope that helps you/others looking for the tutorial from the broken link on http://arduino.cc/en/Main/USBSerial
Hope that helps,