Originally Posted by kovidgoyal
I'm not going to make a portable 64 bit version, 32-bits are portable, 64-bits are not. There are still lots of 32-bit windows systems around. You might be able to get it to work by manually replacing the contents of the Calibre folder in your 32 bit calibre portable directory with the contents of the the Calibre2 folder from a 64-bit calibre install.
I'm not quite sure I understand the logic behind the statement in the first sentence. That said, things do indeed seem to work by replacing the contents with the stuff from the 64-bit version.