Files ending in THMX contain themes that are referred to as Microsoft Office themes. This new feature was introduced in 2007 (Mac 2008) by Microsoft Office.
The designs include predefined styles, colors, fonts and formatting. Unlike traditional templates, THMX designs can serve as a template for documents from various applications, especially Word, Excel and PowerPoint. So it is possible to achieve a consistent look for different documents and document types.
The included themes are in the topic folder inside the Microsoft Office folder.
Own designs can be created with Word, Powerpoint or Excel. In the 'Page layout' tab under 'Designs' you can load, search and save a design.
Most often resolving problems with opening THMX files is very simple. Just install an appropriate program that supports such files. All of the listed programs support THMX files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of THMX files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate THMX files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Microsoft Word applications is not on the list, select "Browse" option in order to manually locate the directory where Microsoft Word has been installed.
Sometimes problems with opening THMX files may not lie with the application itself, but can arise due to other causes, such as: