Bruh all you had to do is temporarily boot into "Disable Driver Signature Enforcement" mode and see IF it boots, if it does then test audio, then try a normal reboot, if it BSODs then just reboot back into "Disable Driver Signature Enforcement" and revert the Realtek driver to the previous version or simply uninstall it entirely, this isn't Piriforms problem your PC crashed because windows apparently didn't want to boot the machine with a new Realtek driver that hasn't gotten approved by microsoft yet, that's literally WHY your pc would refuse to boot (unless via disable driver verification mode).
This driver RTKVHD64.sys causes so many BSOD's for so many people all the time, this has nothing to do with Piriforms product and what it does, next time maybe go search up google about exactly what driver it is, why it crashed and what to do rather than post on the forums saying "DO NOT USE" and scaring people for no reason.
I just updated my drivers, which included Realtek audio as well (yes, RTKVHD64.sys driver is a part of the update) and rebooted just fine. Some people get boned by it, some do not, it's just down to luck and your pc model and age, blame Realtek
bulls**t, see my reply above to the other user, that Realtek driver is always causing problems for people, this isn't a fatal problem done by Ccleaner, all you had to do is boot in "Disable Driver Signature Enforcement" and see IF it does boot and you do have audio, after that a normal reboot should work, if not reboot in that same mode and uninstall the damn drivers and let windows reinstall them instead, it'll be an slightly older version but it'll be a verified by microsoft one so.