While you can download the ISO for free, you cannot activate Windows 8.1 without a valid .
Because Windows 8.1 is end-of-life:
Here is the only safe way to download the official Windows 8.1 64-bit ISO. download windows 8.1 64 bit iso file
While Microsoft has removed direct public links from many of its primary software download pages, there are still two verified ways to obtain the file legally:
Whether you are reinstalling Windows on an older machine, setting up a virtual machine, or performing a clean install, you will need a pristine copy of the operating system. Unlike previous versions, Microsoft makes obtaining the Windows 8.1 ISO relatively straightforward, provided you have a valid product key. While you can download the ISO for free,
If you simply want a working OS, download the instead. It is still supported, faster, and more secure. Your Windows 8.1 key might still activate Windows 10 (though not guaranteed).
You will now be asked to choose the media type. Your Windows 8
You now have the Windows 8.1 64-bit ISO file. You cannot simply drag this file onto a USB drive to install it; you must "mount" it or create a bootable drive.