Update Windows 10 using an external hard drive?

I have the same problem. Have an HP stream and doesn't have enough space for upgrade. I don't get any option to use an external hard drive. I called HP for help and they told me it's a Microsoft problem. 

This is ridiculous that no one from Microsoft can give us step-by-step instructions on how to download the latest version of windows 10 updates. 

Well, it is partially HP's fault as major manufactures like HP and Dell should NEVER have in good conscience sold anyone PCs with 30gb hard drives . They knew full well that they would be unable to support Windows updates, but couldn't bother putting 50gb hard drives in these bargain-PCs instead (which would have made the machines cost all of $50 more apiece).

But ultimately the fault is on Microsoft for flat-out lying to the consumers. "There will be an option to use an external drive to temporarily extend the storage space of your computer while the update is being installed if your device doesn't have enough space for the update. "

NO, THERE WILL NOT BE SUCH AN OPTION. I have worked with dozens of people who have this problem. There is maybe a 2% chance that such an option will be offered. And all over the internet, to the last man/woman, MS techs flat out refuse to acknowledge this fact.

So, for some reason, the 'select external storage' option suddenly and randomly appeared. Out of nowhere, and hours after I had started up and neglected the update prompts for the so manieth time. I have NO idea why or how this happened.

I finally got the chance to select external storage, but the download still wouldn't start. And then I had to wait for this screen to randomly pop-up again, which it eventually did.

Anyway, it turns out that even when using external storage, there still has to be some free space on the C disk.  I had to clear up another 2 GB instead of 8 GB now, which was still a challenge, but after literally deinstallling all removable software (which wasn't much, considering most of it already is on my external storage.. duh) I finally had cleared enough space for this update.

After the update the space I had cleared up was free again... so I could reinstall the stuff I removed but I haven't bothered yet.

Good luck to everyone who's still left in the dark.

Thanks for your reply, but for the sake of saving money since I had just retired, I bought A HP stream notebook. This thing only has 30 gb of memory and 28 is taken up by installed programs necessary to run the software. 

Even when I took half the programs off it only left me with about 5 gb and then with the updated it would be useless. I should have known better and stuck with Dell. 

Now I have to get another laptop and give this piece of junk to a kid do they can play games on it. Lesson learned, it usually pays to spend a few extra dollars then to have the hassle of going with a piece of junk.

I found a work around

Download windows media creation tool for the fall update V1709 from microsofts site,then use an 8 gb usb stick or larger to use on your tablet/laptop after you create the setup files

Once you execute the setup from the usb stick it will guide you through the update and give the option to use external usb storage to update

Fair warning the update took a few hours so make sure the device is charged or plugged in

Hope this helps