Check out the site below for instructions on how to change the display language to French. The display language is the language that Windows uses in wizards, dialog boxes, menus, Help and Support topics, and other items in the user interface.
But you may need to download the Windows 7 language pack. Windows 7 Language packs or MUI packs are used to change the default language of Windows 7 to a language of your choice. For instance, downloading and installing the Japanese language pack will translate all the menus and options in Windows 7 into Japanese. If so, check out this site for all the information you need.