On Windows 7 (or Vista) I use
Free SSL/TLS Certificate Generator (2015/12/15 15:59)
We have published Free SSL/TLS Certificate Generator. This tool is a simple web interface for manual generation of Let's Encrypt HTTPS certificates. Get your trusted HTTPS certficate today for free!
Let's Encrypt is a brilliant project by The Linux Foundation that allows everyone to get a trusted HTTPS certificate for both commercial and non-commercial use forever and completely free of charge. Let's Encrypt project is focused on fully automated generation and management of HTTPS certificates, which requires installation of their client software to your system. Some website owners, however, might run their webs in environments that are currently not supported by the client software, or they have another reason why they can not, or do not want to, install it. For those users, we have created our online interface, so they can simply get their Let's Encrypt HTTPS certificates just using a browser.