Originally Posted by Valloric
If the mimetype file is not the first file and/or is not uncompressed, your epub might not work in all epub-supporting software. Calibre, ADE and Sigil can still handle this, but your epub is still non-conformant and may not work elsewhere.
I usually work from a mac but had to start a new job using a pc in a new job. I am so glad i did. My new books were all ok with epub check and crew flight.
All were unzipped for editing and zipped back up in windows 7 with a right mouse click. The original epubs were generated from indesign epubs. I have never had a problem. No scripts. I knew that the mimetype file was not to be compressed but they just worked.