As you have removed files, then you may need to repair the system.
While a sfc /scannow doesn't check all files, it can repair some corruption, whereas the dism /restorehealth cmd can do much more, but it's best to perform a sfc /scannow after the dism /restorehealth cmd to see that no corruption remains.
This is also the procedure to resolve when a sfc /scannow reports it is unable to repair all corruption in Win 8.1 and Win 10.
What I would suggest is to create Win 8.1 install media if you don't have any and boot up with that.
You can create Win 8.1 install media from
https://www.microsoft.com/en-gb/software-download/windows8ISOYou will need to do this on the Win 8.1 machine.
Boot up with the media and navigate to the Install screen and click on Repair your computer.
I assume you know how to change the boot order ?
I think Win 8.1 will be similar to Win 10 in that you would click on Troubleshoot to select Command Prompt.
At the prompt enter bcdedit |find "osdevice"
For clarity that is a Pipe symbol before find and is the uppercase of \
Using your partition letter instead of the x I have exampled, enter -
dism /image:x:\ /cleanup-image /restorehealth
Disregard what it says about the scratch directory and wait for the cmd to complete.
You can also perform a sfc /scannow with the following cmd, again using your partition letter instead of the X I have exampled.
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
Enter exit to close the cmd window, remove the install media and restart to see if they have resolved.