Windows Vista has an option to change language, as you have discovered, but in Windows Vista Basic it will not change the language in the interface, you need Windows Vista Ultimate for it to work. The ability to change language is for some idiotic reason reserved for Ultimate buyers. So your only options are to either stick with your French Windows, or buy an English Windows. There might be some option to upgrade your OEM Windows to a "real" Windows and the also chnage the language....