Localization: MUI and Regional Options

Source (unattended.msfn.org)

The Multilanguage User Interface (MUI) is used for localizing the OS interface elements (menus, dialogs windows, etc). MUI is not available for retail, and distributed among the volume license customers only. Home users cannot download MUI from the Microsoft web site. The only MUI available on the Microsoft web site is MUI for Windows Embedded. It cannot be used with Windows XP. MUI can be installed on the English Windows XP only.
In this section the Russian MUI is discussed, but the procedures can be applied to any other language version of MUI. There is a total of five CDs with several MUI languages per CD. For example, I'm interested in installing Russian language interface only. First of all, I would like to extract Russian MUI from the CD. This task can be accomplished by creating the Administrative Installation Point. All you need to do is to run setup.exe with the /a switch.

X:\muisetup.exe /a

Where X is the CD-ROM letter. Then follow the wizard and "install" (extract to the specified location) the language you need. This is your MUI installation source that can be used for the installation.
There's only one modification left. You need the updated muisetup.exe. If you have SP2 installed, navigate to your %SystemRoot%\mui folder and copy the muisetup.exe file from there to the MUI installation source (confirm overwrite prompt). If you don't have SP2 installed, you can extract muisetup.exe from the SP2 source (I hope you'll figure out how to do it). Once the updated muisetup.exe is placed in the MUI source, you can prepare for the installation.
...