The Microsoft tool works fine if it's an unadulterated CD/DVD such as an OS one has downloaded from Technet or any Microsoft-made CD/DVD, but the minute anything such as Dell or HP or whatever is included then it fails saying it's not a valid ISO image.
I did see a way to persuade it to work on the web but it failed for me so I'm using method 2 in the link you provided and it seems to be working OK albeit taking several hours. (I just love Vista/Win 7's high-speed file transfer system
although I could probably blame the USB drive in this case).
Thanks so much for your help.
P.S. The 3 hours 22 minutes it originally said it would take has shot down to 1 hour 10 minutes, so there's hope yet that it'll be done in my lifetime.