I have solved the problem, I renamed the two LIB files and then attempted an install. This has worked.
It is worth noting that the install program (before the LIB files were renamed by me) did not create a zzzTmpOldFilesNNNN folder. Currently the index for those folders is at 1111, is it possible that four digits is the maximum suffix allowed in the update program and therefore was unable to make a new folder?
zzzTmpOldFiles1111 contains the library files for 12.17 .
It sounds like you haven't rebooted the machine in several months.
Those folders should be cleaned up after a reboot.
If there are 5 of them already, the installer falls back on the old method where you need to reboot to replace DLLs, to avoid creating more of a mess in that folder. In that case, you should have been prompted to reboot at the end of the install:
Did those prompts appear or did something else happen?
Once you restart the machine, everything should work, and the zzzTmpOldFiles folders should also be removed automatically. (If they are still there after a reboot, you can delete them manually, which should also mean installs done afterwards work normally.)
Have you turned off UAC or set it to never prompt? Or are you launching the installer from a process which already has admin rights?
All those .rra files also indicate that the delete/replace on reboot function of Windows either isn't being run or isn't working for some reason.
Note that if Quick Boot is enabled in Windows — and it's enabled by default despite not speeding things up much and being a bug factory — then shutting down and booting up the computer won't do the file replacement; only a restart will, which is counterintuitive. But if you've restarted as well, and still see those files, then something is wrong with the Windows install.