Due to a design flaw which eliminates safemode as a direct-boot option in Windows 8 and 10, you will have to either take the PC in for service or re-install the OS. The normal fix is to boot in to safemode. This is only possible if you can get to at least the login screen. It sounds as if you can not.
If I mis-read how far you can get, here is how to get in to safe mode on Windows 8.
https://www.digitalcitizen.life/5-ways-boot-safe-mode-windows-8-windows-81
Alternately, if you have recovery media such as a DVD or USB stick you could try to boot off of that.
You can try f2 or f8 during the boot process (as soon as it gets beyond the BIOS initialization), but this rarely works.
This guide is for Windows 10, but they are generally...