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 Windows Media Encoder, and then saving those settings to your hard disk. If you created and saved specific settings in Windows Media Encoder, you can also make those settings available to Expression Encoder, which means you won't have to recreate what may be a complex and specific set of encoding settings that you created.
To use PRX files in Expression Encoder, locate your user folder and put your PRX files in the C:\Program Files\Microsoft Expression\Encoder 3\JobPresets folder.