Indeed the right step has been suggested by "xpcman". Just posting a few more steps in case, they might help:
1. Please start the computer and enter System Setup (BIOS) by hitting F2 key when Dell logo appears.
2. Restore System Setup fields to Defaults by pressing ALT + F and clear NVRAM (if available).
3. Shut down the computer and disconnect all power sources and external devices.
4. Press and hold the power button for 10-15 seconds and then release the power button.
5. Re-connect the power connections only and power on the computer.
6. Start tapping the F8 key and boot to the Safe Mode.
7. Check if you are able login in Safe Mode.
8. If you are able to login in the "Safe Mode", press and hold "Windows key" on the keyboard and press the key "R".
9. Run dialog box will be displayed.
10. Type "devmgmt.msc" (without quotations marks) and hit Enter.
11. Expand "Keyboards", right click the listed keyboard(s) and select "Uninstall".
12. Restart the computer and wait for the keyboard drivers to load.
13. Check the functionality of the keyboard now.
Hope this helps.
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