I'll post this here in case it helps anyone else. I bought a couple of Arduino Nanos from a Chinese site. They did not work when I first connected them to my Windows machine (Vista). At first I thought this was because they did not have a bootloader on them, and I would need to follow a process such as this one. However, this was not the problem. It was that the serial interface on the board was not recognised. The usual installation instructions such as this for installing a driver did not work: the driver was not present in the Arduino drivers directory. However, I found that the drivers from this site worked fine. I used the driver link not the driver installer link. And the Nanos did come with a bootloader.