Instead of editing files directly in the epub file, you can change its extension from .epub to .zip and then extract the files. On Windows XP and later you can do this very easily through the explorer contextual menu command "Extract All". After file editing, zip first the mimetype file (use the explorer "Send to" -> "Compressed (zipped) folder" command). Then add all other files in the zip (just drag and drop them over the zip file). Finally, change the .zip extension to .epub.
The epub format requires that mimetype file should be put first without compression (don't worry Windows will not compress it due to its size) in the epub file. However, ADE as well as my device read epub files even if the mimetype file is not first. In fact, if you do direct editing through the 7-zip utility, it will put edited files above mimetype file and an epub verification would complain about this. So, if you want to produce a strict epub file you should unzip it, edit files and zip it again as explained above.
Last edited by fiery; 11-22-2009 at 04:27 PM.