Incredibly cursed error message that I just got on a work PC trying to launch Task Manager:
"Too many files are currently in use by 16-bit programs. Exit one or more 16-bit programs, or increase the value of the FILES command in your Config.sys file."
...now, that message is pretty cursed on its own (Task Manager is not 16-bit and should not be affected by 16-bit open files limitations), but this is 64-bit Windows 10.
Which doesn't even support 16-bit applications.