I've heavily rewritten this comment to reflect every step I took from a DRM'ed ereader .pdb book to a non-DRM'd, error-free open format transferable to my Sony Reader. All this was done an a Mac ibook running OSX 10.4, with the ereader2html MobiDeDrm script with Python 2.6 installed.
I am not a programmer, but I managed to figure out how to do this in a day or so.
First of all, I went here:. I followed the instructions precisely, creating a new python script named 'ereader2pml.py'. It's very easy.
I ran this script on a protected ereader file. It puts any graphics inside the book into a separate folder called 'outdir', and also placed in there an .html file as well as a .pml file. Pml means 'palm markup language', the layout language used for ereader books.
The pml is just a textfile, with odd characters replacing apostrophes, quotes and dashes and so forth - the most frequently recurring characters were "ì", "î", "í", "Ö", and "ö".
At first I manually searched and replaced on these using TextEdit, then discovered this page, which contains an applescript (scroll down, it has a pink background) for searching and replacing on specified terms in a text document automatically. I copied it, opened 'script editor' in the applications folder, and pasted the copied text into a new document (you can save the script as an 'app').
I then scrolled down the applescript to the terms the script was designed to search on - originally "one", "two" and so forth (the script is designed to pop up screens asking you to confirm what you want each word or character or number to be replaced with).
It's ridiculously easy just to swap the numbers in the applescript for the 'odd' characters I listed above ("Ö" etc). Then you save the script as an app - dead easy, like I say, even for me - and start it.
Once you're in, navigate to the .pml file you just created with ereader2pml, select it, and it'll ask you what to replace each of the odd characters with. After that, it takes a minute or two for it to do the entire search and replace, automatically, saving you a bundle of time and trouble (there may be commercial software out there that does this too, but I'm a skinflint).
It's very important that you also create a folder called nameofbook_img, assuming your book is called nameofbook.pml (ie, exactly the same as the book's title, but with _img added). This folder should go in the same location as your .pml book (you can just trash the html file created at the same time). So if you have a folder called 'ereader hacks' which contains nameofbook.pml, it has another subfolder called 'nameofbook_img' (I got this from ereader's own online guide to palm markup syntax, found after a quick google). This folder is for any images contained within the ereader file. Even if you're not bothered about having them, you're going to need the folder, or the next and final step might not work. Place all the images extracted from the original drm'ed nameofbook.pdb file into the _img folder.
Next: download dropbook, as suggested in the previous link to how to create ereader2pml.py.
Finally, drag the .pml file onto the free dropbook software - it's used for creating ereader files. If there's any errors, it'll show them up in a separate window. Usually they're weird characters like the ones I listed above, where rarer characters like ° (as in 23°) have failed to come across. You'll be able to see what and where they are from the window list of errors and you can then go into the .pml file with TextEdit to change them manually (or alternatively add the new 'mistranslated' characters to the list in your new search and replace script, then repeat the whole process).
If the images aren't in the exact correct folder as I stated above, dropbook won't be able to find them and will return error messages. Not only that, it will probably fail to create the new DRM-free, error-free nameofbook.pdb file you will otherwise be delighted to find waiting for you. So make sure you have that image file.
It took me a while to figure all this out, but once I had, it was ridiculously easy to run further ereader books. I don't think I've missed anything out, and I can't find any difference between the broken .pdb book and the original drm'ed one.
Ok, all of the above is now wildly irrelevant because it turned out I was using an older version of ereader2html (v3.0). I've upgraded to v6, and that does everything I need it to. So I'm 'greying' the above in case anyone makes the mistake of trying to get anything useful out of it. What I will say, however, is that the generated html file seems to work a lot better than the pml file produced by the cracking process.
One other thing - sometimes there are unfeasibly long breaks between sections of a book. I've found the easiest way, personally, to edit this stuff is once you've ported the cracked html into calibre, go to the 'zip' file calibre creates after importing, unzip it, and edit the html file inside, ie deleting multiple paragraph returns or multiple iterations of <p></p>. Then rezip it (remember to get rid of the original zip file), and calibre will generate a new, hopefully improved ebook file with your changes incorporated.