Yeah if you read up he got the english language installed, but since it's still a german (right?) base install the login ect... aren't in english. He just wants to know if he used an english installer if it'd work.
 OH I forgot, a language pack won't change everything. Some things are hard coded into files, such as image files ect... and those won't get changed by a language pack. It's like how some video games that are foreign still aren't 100% english. It's just how language packs are made, it's supposed to be a DB of certain files/phrases that swap out easy. Certain files don't get changed as if he gets an update it'll get replaced anyways. Language files don't get replaced on updates, hence the idea of a "db" for language files.