Windows 10 Anniversary Edition Update Startup issue

[Phonesis]

So I updated to Windows 10 Anniversary Edition last night. All seemed ok.

Boot up this eve and PC is stuck on black screen at login (with spinning white dots). Tried all sorts and cannot get beyond this screen!

The more worrying thing is I can't get into safe mode. I keep rebooting and eventually it opens the Windows 10 troubleshooter where you can select to reboot in safe mode.

When it reboots, I get asked to press a key to decide on boot mode type. The problem is I cannot use the keyboard! It is a USB one and it doesn't seem to work at this point. As if no power is going to it.

So I currently have no idea what to do! Any ideas?

 

[Phonesis]

Update:

So with the help of a PS2/USB adapter I was able to plug my old USB keyboard into the PS2 port of my PC and therefore get into safe mode.

Really not sure what to try next though. If I restart, it ends up on the black screen again unless I reboot in safe mode. Device Manager seems to be reporting everything is OK.

Can I roll back the Anniversary Update somehow?

 

[Phonesis]

Ok so sorted.

It was the Nvidia driver. Some sort of bug with Windows 10 update thinking the driver is installed when it isn't. Had to uninstall the driver in Device Manager from safe mode then reboot. It now boots ok and the driver is installed (?).

Vital lesson learnt for me here is that USB is not powered on boot up so I simply couldn't access bios etc without the trusty PS2 adapter at the ready!