I just realized that you may not know how to get .imp files directly onto your EB1150. If your primary concern is saving books on your hard drive so that you can put them back onto your EB1150 at a later date, this is definitely possible. The .imp file format
appears useless if you are using the Online Bookshelf to transfer books because the Online Bookshelf won't let you upload an .imp file directly, right?
The good news is that you
can load .imp files directly onto your machine either by using
impserve, or by dropping an .imp file directly onto the base directory of a Smartmedia memory card. Using a memory card also allows you to retrieve annotated ebooks from the EB1150, so I do like this option quite a lot. Finding a Smartmedia card for sale is the real challenge, but you can usually snag a pretty good deal on a used 32mb, 64mb, or 128mb Smartmedia card on EBay (for around $20-$35).
Let me know if this helps.