I believe it has nothing related with the computer age. About the viruses... it depends but is most likely has nothing related.
May sound like silly but, check if you are really placing the fhm files on the correct feral heart installation (in the case the old one still around). Try running Feral-Heart directly instead from using the shortcut at the desktop.
All .fh* files should be at "exports" (ex: FeralHeart\Exports ) and not inside any other sub-folder (ex: FeralHeart\exports\map\)
If you still unable to solve this, i can try to solve this myself with team viewer (controlling the computer remotely), but for this you need to find me online ingame.