In a nutshell: Use a combination of Eww and markdown mode, and configure markdown mode to render markdown with pandoc.
Alas, easier said than done.
Update to Emacs 24.5
Eww is the built-in browser since Emacs 24.5 It can be used to display html output. Eww does not run out of the box in Emacs 24.5 for windows. The libxml2 library has to be downloaded and copied manually into Emacs' bin folder.
In order to install markdown mode through the built-in package-manager, you first need to fix the package manager. It relies on TLS. However, Emacs' 24.5 TLS implementation does not work out of the box in windows. To make it work:
First download the GnuTLS libary and copy it manually into Emacs' bin folder.