There are a lot of uses for (Open)PGP - mail, file encryption, disk encryption, digital signatures...
On Windows, there is
Gpg4Win, and that's it. There is Enigmail as a plugin for Thunderbird, which gives decent mail support. For the other uses, if you don't consider Gpg4Win package good, there aren't any good ones for Windows. (Open)PGP integration in Windows is awful, in my opinion. Someone likely wants to explain to me how stupid it is to integrate it in a closed-source OS, by all means go ahead, but I already know how that song goes.