1. Create the folders:
To do this, open up a command prompt (CMD) and enter the following commands one at a time.
2. Extract the ISO and copy the ISO files.
Extract your Windows 8.1 ISO and put the files in C:\provl\dist\ folder.
Then move the install.wim located in C:\provl\dist\sources\ to the new folder C:\provl\wim
3. Open a Deployment tools command prompt
Now you need to open Deployment and imaging tools CMD as administrator and enter the following commands one by one.
dism /mount-image /imagefile:c:\provl\wim\install.wim /index:1 /mountdir:c:\provl\mount
dism /image:c:\provl\mount /set-productkey:GCRJD-8NW9H-F2CDX-CCM8D-9D6T9
dism /unmount-image /mountdir:c:\provl\mount /commit
dism /export-image /sourceimagefile:c:\provl\wim\install.wim /sourceindex:1 /destinationimagefile:c:\provl\dist\sources\install.wim /destinationname:”Windows 8.1 Pro” /compress:maximum
4. Create the EI.cfg file
Don’t close our Deployment Tools command prompt window yet. Now you’ll need to create an EI.cfg so paste the following in to notepad and save as EI.cfg and finally place it in C:\provl\dist\sources\ folder.
5. Create the ISO
Now you’ll just need to create the Windows 8.1 Pro VL ISO file, so open up the Deployment and imaging tools command prompt window again (which I’m assuming you haven’t close yet)
Then type the following to create the ISO in C:\provl\iso
oscdimg -bC:\provl\dist\boot\etfsboot.com -h -u2 -m -lwin8pro_vl C:\provl\dist\ C:\provl\iso\Windows_8.1_Pro_EN-US_Vl.ISO
6. Clean up
When your ISO has been created, you can cleanup and delete the files and folders you no longer neeed.
Delete these 3 folders and you’re done. C:\provl\mount, C:\provl\wim, C:\provl\dist