What should I do if I cannot enter certain characters with my keyboard?

• If you cannot enter numbers by the numeric keypad, check if the Num lock icon in the desktop notification area is green or gray.
  When the icon is grayed out, the numeric keypad works as the directional arrow keys and the Home, Page Up, Page Down and End keys. Press the Num Lk key to change the Num lock icon to green before entering numbers. [Details]

• Check if the Caps Lock indicator light is on or off.
  When the indicator light is on, characters typed will appear in uppercase (or lowercase if you also hold down the Shift key).
  When the indicator light is off, characters typed will appear in lowercase (or uppercase if you also hold down the Shift key).
  Press the Shift+Caps Lock keys to turn the Caps Lock indicator light on or off. [Details]