How do I secure my windows login with google authenticator?

I want to secure my windows login with google authenticator. Preferably by using an open source solution, I want a login mechanism where I just don't enter a username and password, I also have to enter a code to enter. It should be compatible with Windows 7 and later.

Please refer to a place where installation instructions are also present.

P.S. I'm not a fan of hardware tokens so please don't refer that.