Just wanted to share my experience. I have an ASUS laptop E200HA with 32G hard drive.
(So I made the same mistake as most people on this thread by buying this damn thing for my wife.)
I managed to update to version 1803 successfully and still have free 9G on (C) drive.
- Using a different PC, I downloaded Media Creation Tool from https://www.microsoft.com/en-us/software-download/windows10
- Using the tool, I made a (bootable) USB 16G flash drive (formatted in NTFS).
Alternatively, you can download a ISO file, unpack it, and copy to the flash drive.
(It won't be bootable, but you will not need that feature.)
- I moved all my files to a SD card, but I left a few applications on the main (C) drive
including Office 2000, Chrome, e-mail client, and Adobe Acrobat.
- I inserted my USB flash drive and double clicked the setup.exe file.
I chose the option to keep all my files, apps, and setting.
It told me that I had enough free memory (10G) on the USB drive, but I needed
about 4G free memory on drive (C), which as you know is hard to find.
This is how I found it.
I went to (C) -> Windows -> SoftwareDistribution -> Download
and emptied it. I was allowed to proceed with installation.
- Installation went fine without any problems. It took a long time, perhaps, 7 or 8 hours. I deleted Windows.old folder and now have about 9G free on (C)
That's all.
Good luck,
Alex