You’ve just bought mini PC with a small solid state main drive (say 32GB) or you’re trying to run Windows update on an older version of Windows 10 but the later 1809 update fails.
The problem is often because there isn’t enough space on the drive, it needs at least 20GB free.
Phil’s fix Summary:
Step 1 – Relocate the folder where Windows installs updates to a USB stick or external drive that has 20GB free
Step 2 – Temporarily disable Windows update
Step 3 – Use the Window update assistant tool to do the patches for you
1) Move the Windows update folder on your PC – instructions
2) Optional but if you can Right click on the existing c:\Windows\SoftwareDistribution folder, if it’s over 1GB you can safely delete the files. You may find you’ll need to again Temporarily disable Windows update to delete some of the larger files.
3) Download the Windows update assistant – download link
About 1/3 of the way down page look for
“How to install the Windows 10 October 2018 Update with Update Assistant“
As far as I know, past patches are bundled in the 1809 update.
When I get time I’ll update this with step by step instructions & screenshots.