Compare the key locations with a keyboard that works. Some letter keys and, more likely, punctuation and currency keys will be in different places. Simply unscrew the keyboard, pop out the guilty parties and put em where they belong.
However, note that some boards work differently to others eg. on the board I'm using now, shift 3 gives a £ sign whereas on our spare 'puter shift 3 gives a #. Both are made by Compaq!!