If you don't want to install the full suite, look for puttygen.exe under the "Alternative binary files" section.

PuTTY Key Generator: How to Download and Convert PEM to PPK If you are trying to connect to a remote server like Amazon EC2 using PuTTY on Windows, you will quickly discover a compatibility hurdle: PuTTY does not natively support the standard private key format. Instead, it requires its own proprietary format called .ppk (PuTTY Private Key).

Once you have downloaded and opened PuTTYgen, follow these steps to convert your key: Download PuTTY: latest release (0.83)

The most secure way is to visit the official PuTTY download page hosted by Simon Tatham.