Have done tech support myself for years, not disputing they have fkey functions but the keys are not marked as such and the keys which normally marked as such do not work.
The downvote was for 2 reasons -
First in your initial response it failed to recognize exactly what was described evident by response -
"THe issu can be cauesd by curruptd HDD or changes in BIOS" - when post clearly stated HD's were stolen and replaced with new HD's
Second there are no marked fkeys which was stated(included model to view online via google images or whatever to familiarize with to see the actual keyboard layout)
Being a efficient tech requires recognizing the issue exactly for what it is quickly(how personally advanced to upper tier of tech support quickly)
In any case appreciate the attempt to help(the downgrade was not for a failure to resolve)
Will try your suggest about removing battery, but yet again with no designated fkeys on keyboard and using those in location normally as such which have not worked already provides little hope. The fast boot option is obviously enabled, will probably remove new HD's and load windows on a different PC then reinstall HD's to this laptop, windows 8 was the original OS, concerned this will cause an issue since it had been upgraded to windows 10.