After installing these two updates, restart and then check for updates once again.And update(723,7MB) will appear.Hopefully that's Update 1.
I was surprised to hear it mentioned that 17031 may not be the RTM build. Hopefully there will be some confirmation soon.
windows8.1-kb2919442-x64-express it contains 17031 Build files wtf with that regedit key where did it come from :O