Markdownpad is a markdown editor for Windows. Markdown is a text-to-HTML conversion tool. It allows you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML). In other words, its just like Txt2Tags or many of the Wiki dialects.
It's an interesting idea, reminding me of Multimarkdown composer and Marked on the Mac, but it is free. Marked is just $3.99 and provides live preview of Markdown or MultiMarkdown in any text editor (including in MultiMarkdown Composer). NvAlt provides MultiMarkdown preview for free.
Markdown does not do footnotes. MultiMarkdown does—sort of. And Scrivener does MultiMarkdown well.
1. There are many other Markdown editors, like Gonzo, Markdown-Editor, Mou and Wysiwyg Markdown Editor. TextMate can convert Markdown to HTML as well.
2. MultiMarkdown Composer exports directly to HTML, LaTeX, Flat Open Document (.fodt), OPML and RTF.
3. See also ByWord which has a preview mode.