O P
There are many of those DOS programs that do not FULLY work under XP,
Including Wordstar (Try using a serial port printer
with WS5)
I have a Paradox DOS Inventory/POS application that I wrote a long time ago that shelled out to DOS to do tasks that PDOX could not do, Used serial printers (as well as all 3 LPT, for dedicated paper/forms). The last OS it fully work on was W98SE.
While I am not a fan of the current 'Touch Screen' way of doing things, I don't expect programs like Sigil and Calibre to not support those because they "have to" maintain backwards compatibility with an OS over 5 years old