There are several free Linux based password reset discs availible.
I have used some of them mysel several times.
However, most of them will not work on a system installed as EUFI and thats the way windows 8.x is normally preinstalled.
If you use one of those discs on a UEFI system your going to damage it.
So it is important to know how the system was installed.
There is a tool I have not personally tried but I have seen reviews that it works and it does indeed support windows 8.x systems installed as UEFI.
It's part of a larger package but it claims that resetting the admin password is free.
You would need another working system because the program needs to be installed first.
Then you select the version of windows on the system to recover and it builds a bootable CD or flash drive.
It takes a while because it has to download files from microsoft to build it and the windows PE files are part of a very large download. (so I do not have the time to test it).
Check your PM for a link but since I never tested it, if you choose to use it, it will be at your own risk.
I asked you those questions because I wanted to make sure before suggesting this. I never help people with passwords unless I'm convined it is there system and your answer convinced me.
Best of luck.
Dave