My mouse highlights a word and deletes it automatically

What a hassle I was having yesterday with our computer acting up because each time I try to type a letter a word would automatically disappear-be deleted. Now that is something I know nothing about how to solve. Sometimes I will only notice that a word is missing when I proof read my post. So oh, if only I can shout out saying "Help!" and somebody can come to rescue me, I mean help me with such problem. It would be nice. I am not a computer expert to know even a little problem such as that. I was definitely sweating it out, yep; I had a difficult time managing with writing my posts. Anyway, if any of you out there happens to know the answer to my computer problem, I welcome you to share what you know. You never know, you might be able to help me, and that will make me happy. Okay, I have got to go for now. I think I am coming down with something, perhaps a cold since I have been sneezing while I was still in bed waking up. It's the weather; it is looking like it is going to rain today.