Don't know if it will work with a USB numpad, but there's a freeware program called Sharpkeys that I use on my laptop to make the Capslock key into a Windows key. It might do what you're looking for.

eSpeaks' Corey Noles talks with Rob Israch, President of Tipalti, about what it means to lead with Global-First Finance and how companies can build scalable, compliant operations in an increasingly ...