Windows 8.1 update doesn't appear in the store

I lost a lot of time trying to understand why on some windows 8 installation the 8.1 updtate didn't appear. There are multiple reasons why this could happen. But I find I nice and automatic way to detect what the issue is, there a tool from microsoft called "Windows 8.1 Update troubleshooter" that analyze the pc and tell you why it is not appearing. Here the link : http://go.microsoft.com/fwlink/?LinkId=395014 Download it and run it, then follow the instructions, at the end it should say you WHY you don't see the update. Digger

BCDBOOT failure when attempting to copy boot files (and an operating system wasn't found

If you, like me, tried to deploy Windows8 (maybe for 7 is the same) using a wim image and then used the command

bcdboot c:\windows

and you got the message "failure when attempting to copy boot files" probably you are in the situation I was.
I tried to solve using this command:

bcdboot c:\windows /s s:

(where S: is the small system partition) and apparently with success, but after rebooting the machine you got:

An operating system wasn't found. Try disconnecting any drives that don't contain any operating system.

after many unsuccesful test and many investigation, I arrived to the conclusion the issue is related to the UEFI support of the machine (also if when starting, it appears to be a normal BIOS)

so I solved the issue with the command :

bcdboot c:\windows /s s: /f ALL

that ALL means copy both the BIOS and UEFI files to the disk

Remember S is the system partition, not the partition containing windows files