Don't worry! It's only stuff...

# download and extract german language pack
http://drupal-de.googlecode.com/files/de.po.zip
 
# enable locale module
Administer > Site building >Modules
admin/build/modules
check: Locale
 
# install german language
Administer > Site building > Translate interface > Import
admin/build/translate/import
Language file: de.po/de.po
Import into: German 
[Import]
 
# set german to default language
Administer > Site configuration > Languages
admin/settings/language
German: Default
 
 
# Links
http://drupal.org/project/de