I tried to update Windows 10 but I didn't have enough storage so it made me use a flash drive to complete the update. I restarted the computer when it was done, and now it's stuck on a "Please insert external storage media and press OK" error message. I press OK over and over again but nothing happens and the message doesn't go away. I can't get to the desktop. Anyone know how I can fix this?? It happened in the middle of a big project I've been working on =(. Any help would be greatly appreciated!
I know this is an old post but I’ve found a method (from another post by someone else) of
‘undoing changes made to your computer’ snd most importantly recovering important FILES.
You’ll need to download a Windows 10 media boot key onto an empty usb stick. You can do this on another PC directly from the Windows own page . Simply search ‘Windows media boot key ‘ on Google and select the one on actual Microsoft page
Do you have backups of important files & downloads? If not, try this...
(a)
Insert the Win 10 Installation Media.
(b)
Boot to it through UEFI/BIOS, using the
Boot Menu key...
(Press & hold the key at the manufacturer's logo screen.)
On my Lenovo x220 I needed to press F12
The following website shows you Function keys egF12 for different computer manufacturers
Get access to BIOS settings & Boot Menu: F-keys/Hotkeys by System Manufacturer (OEM)
Get access to BIOS settings & Boot Menu: F-keys/Hotkeys by System Manufacturer (OEM)
(c) Click "
Repair your computer" (instead of to install) at the media's 2nd screen (going by Carmack's memory). The computer will reboot to the Recovery Environment at the
Choose an Optionscreen.
(d) Click "
Troubleshoot > Advanced Options > Command Prompt".
(e) Type
Notepad, & hit
ENTER at the prompt.
Notepad will open in GUI mode. Click the
File menu, & select
Open. At its bottom right, set the Open requestor to "
All Files". Now the requestor is a mini-File Explorer. Plug in a different external drive or USB drive, & copy important files over to it. Probably, you want to copy "
C:\Users". There may also be a "
C:\Windows.old\Users" folder to consider. Do not open any huge files in Notepad, just use it to copy them over.
Right click on your mouse or trackpad or plug in a mouse and click send to the external hard drive
After I copied the files over included a huge computer library (and checked I could load the files on another PC from the external drive ) I deleted the huge files ensuring at least 50GB free (I had 14gb free when Windows update failed)
(f) Close the Command Prompt with its "
X", or type "
Exit".
The computer will return to the "Choose an Option" screen.
(g) I guess try "
Troubleshoot > Advanced Options > Startup Repair".
This worked and it rolled back
If not you may need to clean install Win 10 using the Installation Media but you’ll lose all your files so ensure you’ve copied everything off hard drive to external medium first
In 2-1/2 years of playing with W10, I was only able to create a W10 MCT flash drive image on an 8GB flash drive, one time, and haven't been able to repeat that since Microsoft's Anniversary Update release (v1607 b14393.x) in Aug. 2016.
So, we recommend that you 
If you must do this yourself because you can't afford a repair Tech, then at least take sensible precautions with your Personal Data. REMEMBER, ONE WRONG CLICK OF YOUR MOUSE--AND ALL YOUR STUFF CAN BE LOST!! 
A Mac won't work; however, some of our expert Techs have been able to create a W10 bootable flash drive with a 16GB drive using Mac Bootcamp or another virtual terminal type program on the Mac. But Macs vary widely, and unless you have a Mac with an Intel CPU processor in it to run the Windows emulator, I don't believe it will work.
