How can I best create my own custom Windows Server 2012 R2 and Windows Server 2016 ISO's? All I'd need are the official Microsoft ISO's (which I have) with all updates to date slipstreamed into them. It would speed up in-place upgrades quite a bit. I've tried using dism to update the install.wim, but I have 2 issues with that: The install.wim grows quite a lot, from the original 4.4GB to 7.2GB after adding all patches. And running dism with a /StartComponentCleanup parameter afterwards fails because of pending actions. Because the image is bigger we need more free disk space on the servers where we want to do an in-place upgrade. Not a blocking issue, but there's not always enough free space and we need to cleanup/extend the system drive before being able to continue. I used ImgBurn to recreate a bootable ISO, but apparently the ISO is only usable for legacy BIOS machines. Physical servers with UEFI refuse to boot with it. I think I've seen people sharing such custom ISO's, but for security reasons I want to create my own. Then I'm sure nothing else has been slipped in NTLite might be an option, but I'm not sure yet if it'll address both issues. Or other free/cheap tools??