With permission from carminabigue I would like to add a few steps. Please try the below mentioned steps and reply with results:
1. Please start the computer and enter System Setup (BIOS) by hitting F2 key at Dell Logo.
2. Restore System Setup fields to Defaults by pressing <Alt><F>.
3. Shut down the computer and disconnect Battery, AC Adapter and external devices.
4. Press and hold the power button for 10-15 seconds and then release the power button.
5. Re-connect the AC Adapter and Battery only and power on the computer.
6. Start tapping the F8 key and boot to the Safe Mode.
7. In the "Safe Mode" press and hold "Windows key" on the keyboard and press the key "R".
8. Run dialog box will be displayed.
9. Type "devmgmt.msc" (without quotations marks) and hit Enter.
10. Expand "Keyboards", right click the listed keyboard(s) and select "Uninstall".
11. Restart the computer and wait for the keyboard drivers to load.
12. Check the functionality of the keyboard now.
To know more about Dell's products, services and drivers & downloads, please go to http://dell.to/YBlak6