britannica, like some bibles and dictionaries, may be a particularly tough convert even with 64 bits.
So share the source e.g. via dropbox and get a friend to try it before you go to the time and expense of changing your os
or get an epub source ( making the whole thread redundant) ?
it seems ( from googling
britannica epub) you can grab the epub volumes from project gutenberg, with or without images as you please: e.g.
http://www.gutenberg.org/ebooks/34312