Is it necessary to burn a .ISO file to install Windows 8.1 Pro? I can’t find the setup file.
You can upgrade through Windows Update. If you want to download the upgrade as a separate entity, then yes, you can only get it as an ISO file, which you can either burn onto DVD or transfer to a USB drive.
I understand. Please tell , that if win 8 is installed through cd , then can it be upgraded online to 8.1 or because original installation of 8 was through cd then upgradation is mandatorily through cd also?
Yes, should be OK. The update is not related to how the original OS was installed.
Thanks. Please tell whether product key and product code is same or different?
well iso is iso file and not exe file, unless iso was extracted. i think you can also use usb key
you can try to download again
Upgrade Windows with only a product key
Thanks. You mean ISO file is only for upgrading ( not for creating dual boot )
ISO file has first to be extracted to usb or blank dvd to continue installation?
well if your iso file from windows 8 upgrade then yes it is for upgrade purpose.
well you can burn iso file to boot from it and you can try your mentioned way. Myself i used the iso file burned to cd.