http://www.fivenumber.com/install-language-packs-for-microsoft-office-sharepoint-server-moss-2007/
Click Start > Settings > Control Panel, then click Regional and Language Options.
Regional and Language Options In Regional and Language Options box, under Supplemental language support section, check both check boxes
Install files for complex script and right-to-left languages
and
Install for East Asian languages
Click OK to install
Download language packs for Microsoft Office SharePoint Server (MOSS) 2007:
Select the language from Change Language dropdownlist
Available language packs:
Arabic
Bulgarian
Catalan
Chinese (Simplified)
Chinese (Traditional)
Croatian
Czech
Danish
Dutch
English
Estonian
Finnish
French
German
Greek
Hebrew
Hindi
Hungarian
Italian
Japanese
Korean
Latvian
Lithuanian
Norwegian (Bokmal)
Polish
Portuguese (Brazil)
Portuguese (Portugal)
Romanian
Russian
Serbian (Latin)
Slovak
Slovenian
Spanish
Swedish
Thai
Turkish
Ukrainian
After downloading the Server Language Pack.img
Extract the ServerLanguagePack.img file (I prefer to extract using ISO Edit)
Extract the ServerLanguagePack.img Run Setup
After installing the language pack
Rerun the Sharepoint Products and Technologies Configuration Wizard using default settings.(If you don’t run the language pack will not be installed properly)
To run the Sharepoint Products and Technologies Configuration Wizard:
Click Start > Programs > Administration Tools click sharepoint Products and Technologies Configuration Wizard
then click Next
Click Yes in the dialog box.
On the modify server farm settings, click Do not disconnect from this server farm, then Next
After configuration successful click Finish
After success installation, you will be find the language pack which you installed before in the dropdownlist while creating the site collection
Creating site collection Result:
Sharepoint collaboration portal in German language 
HuynhVoThinh's Webblog 