The grx file extension is used by GetRight Download Manager for Microsoft Windows system and used for files that contain saved file list.
These grx files probably contains list of files for download.
How to open:
The *.grx files are used for internal purposes GetRight.
How to convert:
As far as we know, this .grx file type can't be converted to any other file format. This is usually the case of system, configuration, temporary, or data files containing data exclusive to only one software and used for its own purposes. Also some proprietary or closed file formats cannot be converted to more common file types in order to protect the intellectual property of the developer, which is for example the case of some DRM-protected multimedia files.