Dedup was a server feature that they changed around to be able to run on Windows 8.x x64 I don't see it being able to be re-created until the next server build is available. I imagine it requires a decent amount of work. It's not something you'd waste your time on a preview build for.
Just follow murphys link in post #6 and download the iso! If this is done, read my previous post and extract the required files. After that's done, install the server feature on your windows-x preview.