Updating Windows 10 on a low-internal memory computer.

[SamWright]

I am trying to update Windows 10 on a low-internal memory computer. Following the article which I found on this site, I have used the media creation tool on another computer to download the latest installation files onto a USB flash drive, plugged it into the computer in question, and then double-clicked setup.exe. There is also another empty flash drive plugged in to provide temporary storage during the installation. Eventually there is a message to say that ‘Setup failed to validate the product key’. Where do I go from there?