(a) Disconnect the external keyboard and then see if it works.
(b) Try to lower the acceleration at start > Control Panel > Display Properties> Settings tab > Advanced button > Troubleshoot tab > Hardware Acceleration slide.
(c) Create a new user account and check. If it works in a new user account, then probably your user account may have been corrupted and would need a fix.
You can also try to disable and enable the onscreen keyboard and check if it works fine or not. To do so follow steps:
1. Press the Win + U keys together to launch the Ease of Access Center.
2. Then click on “Use the Computer without a mouse or keyboard” (most probably the 3rd option in the list).
3. Then on next page uncheck the box which says “Use On-Screen Keyboard”.
Run a system file checker if nothing works and also run a full updated antispyware scan in your system.

Here’s to Good Karma