“Fix” is a bit of a loose term for this solution because it will restore your computer to a workable state without losing any files or applications, but you have to disable Windows Updates so the affected update doesn’t continue to be downloaded over and over again.

Update: There is now a patch out to fix this: https://support.microsoft.com/en-us/help/4090913/march5-2018kb4090913osbuild16299-251. Note that when I checked for updates using Windows Update, it downloaded the bad patch again, so I uninstalled that and downloaded the patch linked from the article above (Actual link to download the update is http://www.catalog.update.microsoft.com/Search.aspx?q=KB4090913).

If you encounter the blue screen of death with the message “Inaccessible Boot Device” and a frowny face, you’ve probably just updated Windows and the computer attempted to reboot.

I will not take any credit for this fix, as I spent several days looking for ways to resolve this problem when it affected machines in my office. A huge thanks goes to reddit user zosan for providing this excellent, step-by-step guide:

How-To: Fix "INACCESSIBLE_BOOT_DEVICE" caused by Win10 Spectre builds 16299.125 or 16299.192. from pcgaming

Hopefully Microsoft resolves this sometime soon so updates don’t have to be disabled too long.