Sorry Martin, I really thought you'd solved it but your diagnosis doesn't seem to work on my machine. I've got two hard drives, one of which is split into 4 partitions, plus a zip drive. I copied the seed file to C, D, E, F, G and I and put the pcf file on G. (D is the totally different hard disk and I is the zip disk). It decoded perfectly every time. Back to the drawing board.