Thanks, Susan. I did read that - several times, in fact - but I was still at a loss. I eventually found this page which was a bit more expansive:
http://www.helenhanson.com/kindle-fo...-exe-–-part-6/
I have now managed to get Kindlegen to run and produce a .prc file. However, although I put the file to be converted on to the desktop I could not find the .prc file there, so I had to run a search for it, and found it in My Documents\My Publications. Is there any way of altering where the output is saved to?