French pack for Magento 1.8?

Question

I am trying to install a French pack for my store and I am on Magento 1.8. The default language for my store is English.

And this is link of the French pack that I found,

http://www.magentocommerce.com/magento-connect/magento-community-modules-french-france-language-pack.html

But it does not work on my store.

Does this pack compatible with Magento 1.8?

What can I do to have a French version for my store if this pack does not work?