If the books are already in .lrf format, I don't think they need to go into ADE, I think you can download them to any folder. I have done this & transferred them using the Sony library software. I've only used ADE for the couple of books that I've bought so far from Waterstones (using the points accrued from buying the reader, so effectively free
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I downloaded the US software, so that I could access the Sony US store - even if you don't buy from there, I think it is worth doing. You don't need the UK version to buy from Waterstones, and in the couple of months I've had the reader, I've downloaded quite a few free ebooks following tip offs on here
The free books were on a CD, rather than pre-loaded, although there were a few things (mainly samples) pre-loaded.
Enjoy your reader