Well, I've burned two would-be DVDs using Picasa.
Neither are recognised by the dvd player, probably because the slideshow - with added music track, is saved in a .wmv format.
Why the disk created by the program itself is not recognised by the dvd player I've no idea. But it just says "disk error". (this is the "create gift cd" option within picasa.)
Sad to say, I did not find this a doddle.