Why am I typing the wrong letters?

Q The keyboard of my Windows 7 laptop has become unusable. Many keys type the wrong letter when I press them.

Typing ‘m’, for example, results in a ‘0’. I have struggled to write this email, copying and pasting some of the letters from old documents.
Ahmed Mostafa

A We believe this issue is probably related to the Number Lock function on your PC.

The two clues here are that your PC is a laptop and the example you gave, of ‘m’ typing a ‘0’. First, many laptops have an ‘embedded’ numeric keypad, to mimic the separate keypads that are a feature of most full-size, desktop keyboards. Second, laptops that feature these embedded numeric keypads start with the ‘0’ on the ‘m’ key.

At some point, you must have accidentally enabled the Number Lock mode, so these keys now function as number keys, rather than the letters that more prominently appear on the keytops (if you look closely, we think you will see that the ‘m’ key also has a ‘0’ label, in a less-noticeable colour).

You didn’t tell us the make and model of your laptop, so we can’t give you specific instructions for switching the Number Lock function off.

However, typically there will be a ‘function’ key (labelled ‘Function’ or ‘Fn’) that must be held down while tapping a second key labelled ‘Num Lock’ or ‘Number Lock’ (or possibly just an icon of a lock with a number in it).