Things to try:
System Properties Refresh Button
(1) Go into System Properties / Device Manger
(2) Click the + sign next to Keyboard
(3) Select your keyboard
(4) Click the "Refresh" button
(5) When the hour glass closes, click OK on the Systen Properties window and try your keyboard.
Look for new keyboard driver
If your keyboard is a "Multi-media" type, you may find updated drivers for it at the manufacturer's site.
If the keyboard is a standard keyboard, you could try removing it from the System Properties / Device Manger and then restarting your computer. Windows Plug 'N Play should automatically reinstall the keyboard driver, although it might prompt you to insert your Windows CD.
I hope something here helps!
Dwight