Keyboard typing random keys

My keyboards has begun typing random things on me. I currently can't tell exactly what it's typing, because I can't get past the password section when I startup. However, when I press most keys, I get two character symbols appearing where I type. When I press delete, it appears to delete a character but then it replaces it with another, so I end up with the same amount of characters. Also, when I press '1', it increases the volume. Have reset the keyboard and changed batteries. Nothing has worked so far.