I installed PuTTYgen on Windows using: putty-64bit-0.79-installer.msi (which I downloaded from the official PuTTYgen website).
Except that when I go to Windows cmd and run puttygen -V, I get the error "Unrecognised option -V". What's worse is that this message is displayed regardless of the option entered.
I have to use PuTTYgen as a batch script without going through the interface to transform an id_rsa file into id_rsa.ppk.
Windows PuTTYgen is mostly GUI only. It seems that you expect it to support the command-line options that Linux console puttygen does. It does not.
Instead, you can use WinSCP console, which supports some console puttygen functionality:
winscp.com /keygen id_rsa -o id_rsa.ppk
WinSCP does not support the -O switch, but the -O private is the default (and the only) conversion it supports.
(I'm the author of WinSCP)
For other options, see:
How do you convert an SSH private key to a .ppk on the Windows command line?
