When you purchase Windows 8 Pro from MS,downloaded it and you've built your final iso with Windows 8 Upgrade Assistant you will have in the sources folder an install.esd, instead of install.wim. Here's how to "convert" the esd to a wim. Files needed: 1. Your windows 8 upgrade iso of course 2. VMware-player-5.0.2-1031769.exe 3. Vmdk2Vhd-1.0.13 4. Win Toolkit 220.127.116.11 5. Win 7 WAIK or Win 8 ADK - deployment tools only Let's Begin: If you are on windows 7 install waik and if on windows 8 install adk deployment tools only needed. Install donet.3.5 sp1 on win7 or enable it on win8 by running cmd as administrator with command: Dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:E:\sources\sxs /LimitAccess, and hit Enter. Where E: would be path to your mounted win8 iso or your win8 dvd. Install VMware player then install your windows 8 upgrade as virtual machine in it. Once win 8 is installed navigate to C:\Windows\System32\Sysprep on virtual machine and run sysprep.exe select the Generalize checkbox and Shutdown in shutdown options. Now press OK and wait for the machine to completely shutdown. When virtual machine has shutdown close VMware player. Note: If you wish to make any changes in your win8 virtual machine do it before you run sysprep. We have to convert our win8.vmdk to win8.vhd so open Vmdk2Vhd to convert it. The conversion here should not take very long, for me it was quick. Now mount your newly made win8.vhd file using the windows built in disk management tool as read only. Right click Computer icon on desktop and select manage then select disk management. Click on Action menu and choose Attach VHD to mount the vhd. To detach your vhd right click Disk 1 (or whatever your attached Disk number is) and choose Detach VHD. Open wintoolkit select Tools tab, select New WIM click Save and type install.wim and save to drive C so it would be WIM: C:\install.wim. Click the Capture Image button then click browse in folder to capture section and choose your mounted vhd drive. So if your vhd is mounted as drive H your folder would be Folder: H:. For Image Name put: Professional x86 For Image Description put: Professional x86 For Flags put: None Leave compression method as maximum. Click start and wait for it to finish capturing your new install.wim - this part could take awhile, for me it took about 45 minutes to complete. Once finished close wintoolkit. Copy your new install.wim to your sources folder and delete the install.esd. You're done! Tutorial written to be easy as possible for average pc user. I hope it will be of help to someone!