If you are looking for a "free" OS for an older x86 machine, consider a lightweight Linux distribution like Lubuntu or Linux Mint XFCE . They are free, legal, and much faster than Windows on aging hardware.
Modifying system files to force activation often leads to "Blue Screen of Death" (BSOD) errors, broken Windows Updates, and driver incompatibilities. full windows 81 pro vl x86 multi6 esd preactivated free
If you are looking for this specific version, you are likely looking for a very particular build of Windows 8.1: If you are looking for a "free" OS
If you need Windows 8.1, there are much safer ways to handle your OS needs: broken Windows Updates