The Non-functioning USB Keyboard.

 

 

 

 

 

 

A customer contacted me recently with what appeared to be a simple problem to rectify. Their USB keyboard had stopped working.

Simple fix, right?

Most likely a faulty keyboard or a driver issue, right?

Not today.

My customer was kind enough to bring their desktop and keyboard to me for further testing and here are my first observations.

• The keyboard was indeed not working.
• The LED’s on the keyboard for caps lock, num lock and scroll lock were also not working.
• Device Manager showed no driver issues at all.
• A USB mouse worked fine.
• All of the USB ports worked fine with a USB mouse.
• The keyboard did work normally in the bios.
• The keyboard worked perfectly on another PC.
• A known working keyboard also did not work on this desktop (in Windows.)

Reinstalling the keyboard driver did not work.

Removing and re-detecting all the USB devices allowed the keyboard to work again until it was restarted or turned off at which point the keyboard did not work again.

At this point, I tried a wireless keyboard, and this also did not work – even though the usb dongle was detected and driver installed.

The desktop in question had no PS/2 ports so I was unable to try those.

Now I am beginning to think that we have a deeper routed software issue at hand and being as the machine was still running Windows 10 ver 1803 I decided to update it to 1809 hoping that doing this would, in turn, fix the keyboard issue.

Nice thought but no dice. The keyboard issue persisted after updating to 1809.

SFC /scannow was unable to find any issues with the windows files so I manually removed the keyboard drivers and made Windows go and get new copies of those driver files.

This also did not work.

Head scratching time

I am now thinking that perhaps there is something going on in the registry causing this that did not get fixed by the 1809 update so off to google I go.

A quick browse around got me the following three registry keys to check.

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96B-E325-11CE-BFC1-08002BE10318}

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\Class\{4D36E96B-E325-11CE-BFC1-08002BE10318}

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96B-E325-11CE-BFC1-08002BE10318}

Only two of these existed on this desktop and the entries looked fine.

However, removing these two entries, removing the keyboard, restarting the system and manually re-creating these keys led us to having a fully functional keyboard again. My theory is that there was some corruption in the registry keys and removing and re-creating them fixed the issue.

This registry key fix does remind me of an issue that used to occur under Windows XP where CD Rom drives would vanish. Removal of two Upper filters registry keys and a reboot would usually fix it. The problem was caused by cd writing software altering the registry keys.

Perhaps something similar happened here.