Hi, here is mi issue, every time i try to install Windows 8.1 from 8 i come across the same problem. When it needs to restart the laptop, it never gets again to the user/password menu unless you restart and loose the update. Please, ive tried many things and still doesnt work, ive waited more than 2 hours and still no response. 

never gets again to the user/password menu 

What exactly are your symptoms?  E.g. some see a blank screen which apparently only means that the monitor that you are looking at is being seen as the secondary of an extended pair.  In that case pressing Win-P, CursorUp, Enter as if you could see and use a Project menu (which would be rendered on a phantom monitor) would switch your Display mode to Duplicate and thus allow anything that was being shown on the phantom monitor to also be shown on yours.

Also it may help to activate Narrator.  I don't know if it can be as easy as pressing Win-Enter in a Login screen context but otherwise you could have a hairy blind navigation to get from the Login screen's Password field to the Accessibility menu button and open that and then activate Narrator in there.  Etc.

Another possibility would depend on whether you had installed any system modifications such as a third-party Start Menu replacement.  It would be best to uninstall such software before trying the install the update.

BTW a workaround for the video issue may be changing your boot options to boot in Low res video.  E.g. that could result in a different driver being used and less likelihood of an extended Display being created.

 

HTH