

Green Gandalf wrote: "My desktop uses Windows Defender"


...no, sorry for the bad joke.
for DirectX, i always install it normaly so that the files sit inside the system32 folder. i never liked to tinker with dll files.
if you download DirectX 9.29 from microsoft, it is a self extracting exe. after extracting, in the target folder there is the actual setup that will install it like normal.
Green Gandalf wrote: "That seems very similar to what I've already tried to no avail."
i cannot think of anything good and easy that you could try.
you can try to make a rollback to an earlier version of windows 10 and then update again.
do you use CCleaner? i had a problem on windows 7 after a registry cleanup that made my explorer crash everytime i rightclick on an explorer window. stuff like this should also be fixed after a rollback.
for a fresh install,
1st: backup all your files to an external drive and then unplug the drive (save remove) so you do not overwrite it later,
2nd: download the windows 10 iso. make sure it is the correct version (Home, Professional, 32bit, 64bit).
3th: make a bootable usb stick or burn a dvd from the iso file. put it in you computer, restart and make sure the computer boots from the dvd/usb drive. if you managed to start the installation, you just need to follow the steps. you can watch a youtube video for a better explanation.
after a fresh install, you should make a backup and if something like this happens again, you can restore the backup and you do not need to make a complete reinstall.
i just realised that my laptop came with cortana disabled, which is enabled by default on a fresh windows install. since we already talk about oddities, you could try to disable cortana if it is enabled on your systems. and see if this fixes anything. just a lame guess from a guy that is out of ideas