This weekend I worked on a Toshiba laptop with Windows 8.1 that had received some updates then rebooted. The keyboard and mouse both failed to work after the reboot. An external USB mouse worked but the USB keyboard did not.
I used the on-screen board to do everything with mouse clicks detailed below. I used the working mouse to access the ON-Screen Keyboard. Windows 8/10 this is under Settings / Ease of Access. Windows 7 it is under Accessories / Ease OF Access.
From this On-Screen Keyboard, Click the Windows key and then Click the letter R to open the run box. Click out the word REGEDIT and click enter.
Navigate to this KEY:
Find UpperFilters, of the type REG_MULTI_SZ. You may have to manually create the key if it does not exist. Edit the value UpperFilters to read kbdclass. If you find other text in this field, delete it and click out of kbdclass. Click O.K. You may get a warning but accept that and move on.
To fix the mouse follow this:
Navigate the registry to this KEY:
Find UpperFilters, of the type REG_MULTI_SZ. You may have to manually create the key if it does not exist. Edit the value UpperFilters to read mouclass. If you find other text in this field, delete it and click out of mouclass.
Exit the registry and reboot. This restored keyboard and mouse function to the laptop.
G’Day to ya!