Summary: Bought this for my two year old. I set up a computer for him and the standard mouse was just to big. This one is perfect for him. He was able to use it right away. I did find it difficult for me to use if I'm trying to help, but I have big hands. I just installed a wireless mouse as well and I can turn it on if I need to help him. One of the reviewers said they were having problems with MS Vista.