SOLVED: VirtualBox shows only 32-bit guest versions on my (64-bit) Windows 10?

I quickly pressed Windows Key + q to open the Search box and typed in: turn windows features on or off Turn windows features on or off I scanned a few options but one in particular was salient: Hyper-V was enabled.

So I installed the 64-bit version of Docker for Windows after configuring a shiny new VirtualBox CentOS 7 guest. The latter’d ran just fine previously, but was now causing a BSOD, and I wasn’t even able to create new 64-bit guests.

As it turns out, installing Docker enables Hyper-V, but uninstalling Docker doesn’t disable Hyper-V; i.e. these virtualization technologies are incompatible. The fix to this is quoted above: disable Hyper-V.