You should download version 3.48.0 , as newer versions require library updates not present in these older systems.
The official developer, Kovid Goyal, maintains an archive of older builds to ensure compatibility with older hardware and operating systems. calibre 32bit download
Most modern PCs are 64-bit, but 32-bit (x86) versions are necessary if: You should download version 3
: A great alternative that runs from a USB drive and often maintains better compatibility across different Windows versions. Why use the 32-bit version? You should download version 3.48.0
Version 1.48.0 is generally the final stable release for this legacy platform. Official Download Links
The last dedicated 32-bit release was version 5.44.0 .