I've spent alot of last week watching the Build 2014 Keynote Videos. Tuesday became my "Happy Day" as the Windows 8.1 Update arrived. I'm digging the cool features like windows "Modern" apps and feel a "must install now desire" to udpate a bunch of machines to put the update through it paces.
I hop on over to my Windows Update area ( WinKey+C -> Settings -> Change PC Settings -> Update and Recovery -> Windows Update ) and check for updates. I'll just start installing Windows 8.1 Update for x64-based Systems (KB2919355), aka Windows 8.1 Update, right? But I've been naughty, and have a ton of service packs and KBs waiting to be installed. OK, install a ton of SPs and KBs and *bs.*.... All the stuff you just push down, right.
Somewhere in the process of udpating I'm sure what state my machine is at. I'm also not sure if I've got Windows 8.1 Update on my machine. Which begged the question, "How can I tell if a machine has Windows 8.1 Update or not?".
Go to the start screen and look for the search button and new power button on the Start Menu. See those and you're good to go. Hope this helps someone. If it doesn't install this easy for you look for my next post about cryptic messages when updating and such.