Support of PRX files
A PRX file contains encoding settings for a video. You create PRX files by applying encoding settings, such as bit rate and video size, to your video in Microsoft Expression Encoder or Microsoft Windows Encoder and then saving those settings to your hard disk. If you created and saved specific settings in Windows Encoder, you can also make those settings available to Expression Encoder, which prevents the need to redo what may be a complex and specific set of encoding settings that you had created in Windows Encoder.
To use PRX files in Expression Encoder, locate your user folder and put your PRX files in the Expression Encoder/Profiles folder. Note that if you save files to this folder while Expression Encoder is running, you must restart the application in order to view the newly-added PRX files.