Product Picture change on Hover

I am using Magento 1.9 with the Classic Theme. Now iam trying to do this:

When iam on a Product, i have the bigger Images and a few small Images. Now when i hover the small Pics, nothing happend. I want if if hover the small Pics, that the bigger Picture is changing to the picture a hover on.

Can andybody help me out with that? Iam already trying this for about 10 hours.....

Kind regards Helle

Photoscape you try to change your image. It's also a pretty good tool