You will need 4 sets of tools :
1. "
Calibre" or some other tool which can convert between multiple types of eBook, including HTML.
Anyone wanting to convert books presumably has this program anyway... essential software.
2. "Sigil" for correcting & editing ePub ebooks
3. Python 2.6 (not 2.7 or later afaik)
4. DRM tools downloaded from links posted in the following thread :
DRM Tools Archive
Use the Topaz tools from the above download in option 4. Unzip them, and search the directories for the Topaz one.
There is a Readme text file included with the Topaz tools that explains clearly how to use them - they have a GUI interface.
The result of the Topaz DRM removal tools is a "book.html" with an associated CSS style sheet file, and an "img" directory with photos, illustrations, etc.
In order to convert to another ebook format, I had to drag the "book.html" file in to
Calibre which 'converts' it to a Zip format ebook; Then I had to select/download a Cover image for it, and convert it to ePub format....
However, this process is not perfect, and each of the 3 books I extracted using Topaz tools had some errors in them when they reached the ePub format in Calibre. Some characters in headings only were mis-translated making nonsense words, and hyperlinks in tables of contents were consistantly "off-by-one" in linking to the wrong chapters... (also, only black and white images were extracted for some reason, apart from the cover)
So I had to use Sigil to edit the resulting ePub book in order to tidy up the files, and correct mistakes in the Table of Contents. Once I had cleaned up this drm free, converted epub format, I could then convert back to drm free Mobi, etc. etc.