Bulk Convert OpenSSH private keys into Putty's PPK format in Powershell
Convert openssh keys into ppk putty keys Requires recent version of WinSCP, specifically winscp.com not winscp.exe puttygen on Windows does not have the command line functionality of puttygen on Linux
ssh-keygen can convert putty public keys apparently but I haven't tried this and I needed to convert already generated private openssh keys to ppk.