I decided the other day to install calibre on a Toughbook running w7pro. The download page hints me to use 3.48 as the most recent version.
I installed it, of course it worked, but suffered from the same issue as another 3 version I used in the past (maybe 3.2x or 3.1x??) namely the text was forcibly italic with some fonts. I put at a time this question in the forum, anyway the only way to get rid off it was to upgrade.
So I used 4.20 on my w7pro, and have no issues so far. This also reminds me of one of my first questions here (unrelated to windows) when I was replied that whatever 2.x version won't work on my XP although I used it for months
To sum things up, how is indicated that a version works or not or it is "indicated" for a particular platform?