The markdown format is increasingly used at websites like GitHub. Thus, there is a need for a simple markdown editor that can be used to edit and view markdown files.
MarkdownPad is a markdown editor for Windows which I found does this job well. Just download and install. Associate .md files with MarkdownPad, which can be found as
MarkdownPad.appref-ms in the directory
Tried with: MarkdownPad 126.96.36.199 and Windows 7 Professional x64