MSDN Universal Subscribers get Expression Encoder for free
Juts use the key you have for Expression Studio delivered on MSDN Subscriber Downloads, on the page Subscription Product Keys.
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We are pleased to offer Expression Encoder, formerly Expression Media Encoder, for download. If you are an existing Expression Studio or Expression Media customer, please enter your Expression Media (Windows) product key when prompted during the Expression Encoder installation to activate the software. If you do not have a product key, you can download Expression Encoder and preview its functionality. This fully functioning version will expire 60 days after installation. – Jonathan [MSFT]