This is the encrypted esd file that is downloaded by Windows Store when upgrading from 8.0 to 8.1. Luckily a few awesome guys at MDL worked out the decryption process and made up a script with a few options.
Instructions:
1) extract the 7z file to same directory as esd file
2) run admin command prompt and navigate to the directory
3) run decrypt esdfilename
There's not really any benefit to using wim file over esd file unless you need to modify the installation. ESD file is faster and smaller. WIM file is mountable, but larger.
