An MSH1XML file is a configuration file used by Monad, a shell program included with Windows in 2005 and 2006 before being renamed as Windows PowerShell. It contains XML definitions for how output is displayed within the console. MSH1XML files are used for formatting various output, such as help pages, registry information, and directory listings.

MSH1XML files were introduced when Monad was released in 2005. However, they were soon replaced by .PS1XML files in April 2006 when Microsoft renamed Monad as Windows PowerShell. Since MSH1XML files store the configuration information in XML format, they can be easily opened and edited using a text editor. However, you should only edit the files with the proper knowledge of the content.