Here is what you want to do to get MOSS to be multilingual.

First, you want to check that you meet the prerequisite: Additional Language File Support.

1. On your front-end Web server, click Start, point to Settings and then Control Panel, and then click Regional and Language Options.
2. In the Regional and Language Options dialog box, on the Languages tab, in the Supplemental Language Support section, select one or both of the following check boxes:
   Install files for complex script and right-to-left languages
   Install files for East Asian languages
3. Click OK in the dialog box that alerts you that additional disk space is required for the files.
4. Click OK to install the additional language files.
5. When prompted, insert your Windows Server 2003 product disc or provide the location of your Windows Server 2003 installation files.
6. When prompted to restart your computer, click Yes.

Then you want to install the following components in the following order for each language:

(Use the change language drop down to choose different language’s language pack download)

1. WSS Language pack (SharePointLanguagePack.exe)
2. WSS Language pack SP1 (SharePoint.exe)
3. MOSS Language pack ( extract *.IMG file)
4. MOSS Language pack SP1 (officelp2007sp1-kb936982-fullfile-it-it.exe)

Warning and remarks! The only bad thing about all this is that you need to know all this before you start creating Site Collections because you can install new site in languages you later installed. I have learned that!

Also you may need to update WSS to SP1 prior going to step 2 as described in kb945967. Find it here.

The other bad thing about SharePoint is that you have to do the install on each "role" server of the farm. I wish there will be some central update managemet for SharePoint sometime soon!