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

• Check if the Caps lock indicator light is on or off.
  If the indicator light is on, characters appear in uppercase when you press a key without holding down the Shift key. Press the Shift+Caps Lock keys to turn off the indicator light, and then you can type characters in lowercase. [Details]

• Check if the Num lock indicator light is on or off.
  If the indicator light is on, you can type numeric characters printed on each key on the keyboard.
  If the indicator light is off, you can type alphanumeric characters printed on each key on the keyboard.
  Press the Num Lk key to turn on the indicator light. Press the key again to turn off the indicator light. [Details]