I have found a solution for this, 3 edited files.
But these files are edited for a previous version of Magento, I don't know which version.
I have uploaded this 3 files on my Magento 1.7 and it works but when add the product to the cart it give's a error with app/code/core/Mage/Sales/Model/Quote.php
This file: Quote.php is one of the edited files, when i upload the original Quote.php it works.
Look at this pic: http://s8.postimage.org/g8bvbth0z/Naamloos.png
But maybe i get more errors in the future, i don't have any ideas..
I am a noob with this, if someone can look at the edited files and chek how they have do this and compare this with the newest files for Magento 1.7 maybe we can help to many peoples with this problem.