My Keyboard auto deletes everytime I type numbers

Hello,
Can someone advise me on what to do? I use HP laptop with Window 'SEVEN' operating system. I cannot type numbers because the keyboard deletes the texts preceeding it. This not only happens with microsoft office documents, even now as I type, this message has been deleted two times, hence the 'SEVEN' in this message as the number cannot be typed without deleting this message. I cannot open my emails on this laptop. How can I fix this?