Administrators like to set international settings from the command line.  (Ie: Regional and Language Options, aka intl.cpl options).  It is possible to do this automatically in Windows Vista through an xml configuration file.  A document is being created for MSDN, but I thought I'd provide a preview of how this can work.

Basically you just create an xml file with content like this:

<gs:GlobalizationServices xmlns:gs="urn:longhornGlobalizationUnattend">
    <!--User List-->
    <gs:UserList>
        <gs:User UserID="Current"/>
    </gs:UserList>
    <!-- User Locale-->
    <gs:UserLocale>
        <gs:Locale Name="es-US" SetAsCurrent="true"/>
    </gs:UserLocale>
</gs:GlobalizationServices>

And then send it to intl.cpl by using the command:

control intl.cpl,, /f:"intlsettings.xml"

Where "intlsettings.xml" is the full path to your xml file.

This example changes the current user locale to "Spanish (United States)".  The full documention will show how to change other Regional and Language options settings as well.

I'll post again when the documentation's available on MSDN.

[1 Jan 2011: see http://msdn.microsoft.com/en-us/goglobal/bb964650]