Markdown Monster Portable
A portable installation of Markdown Monster can be run from any location without any further dependencies except for the following Markdown Monster system requirements:
- Windows 10-7 or 2016-2008R2
- .NET Runtime 4.52 or later
- Internet Explorer 11
Limitations of the Portable Version
The portable version of Markdown Monster is fully functional and provides all the features you have in the fully installed version except:
- .md and .markdown file Associations are not configured
Manually registering .md and .markdown Extensions
Right click on an .md file, use Open With..., Choose another app, then select Markdown Monster (if it shows) or browse for the MarkdownMonster.exe executable. The check Always use this app to open .md files.

and then choosing Markdown Monster:

Most likely you will have to explicitly search for the executable rather than pick off the list, but the process is otherwise the same.
Once selected, .md documents should now open with Markdown Monster.