Mozilla has a solution for you: See Change Default Mozilla Language.
A language pack is an extension that
changes the language of the user
interface in a Mozilla application
(Firefox, Thunderbird, SeaMonkey,
etc.).
Downloading a language pack
To download a language pack:
- Go to: http://releases.mozilla.org/pub/mozilla.org/
- Go to the directory there for the Mozilla application you want to change—for example: thunderbird
- Go to the
releases directory.
- Go to the directory for the release you are using—for example: Thunderbird 1.5.0.8
- Go to the directory for your operating system—for example: win32
- Go to the
xpi directory there.
- Install the xpi for the language, or language and region, that you want. For example, the French language pack is: fr.xpi
Note: To install a language pack in Thunderbird, do not click the link to the xpi file. Instead, open Thunderbird's Extensions or Add-ons window, then drag the link from your browser and drop it there. Alternatively, save the xpi file on your computer and install it in Thunderbird later.
Assigning a language to a profile
To assign a user-interface language to a profile, set the preference general.useragent.locale to the name of the locale that you want to use. The name of the locale is usually the same as the name of the language pack that you installed (without the .xpi extension).
For example, to use French you can specify the locale as fr or fr-FR.
Note: If you often switch locales, there is a Locale-Switcher extension to make it easier.
Assigning a language in a command or icon
To assign a user-interface language to an icon that launches your Mozilla application, look in the icon's properties to find the command there.
To assign a user-interface language in a command, add the switch -uilocale followed by the name of the locale.
For example, to use French you can specify either: -uilocale fr or -uilocale fr-FR. On a Windows system the entire command might look something like:
"C:\Program Files\Mozilla Thunderbird\thunderbird.exe" -uilocale fr
Am I just setting up my system incorrectly?
In a way, yes. You certainly aren't reading the tab that you are looking at.
This is is a quick, dirty, incredibly lazy way to guess language settings that's probably right 99% of the time.
Wrong. The installer programs are using the Windows National Language Support API to obtain the system locale and language that you've configured, to determine what language to prompt you in. The locale information is set with the "Formats" tab in that part of Control Panel.
You're using the "Location" tab. Locations are different to locales and languages, not least because the .NET API for them doesn't really function on Windows prior to Windows NT version 6.1. The locations API is a completely different one, that doesn't even exist on Windows XP prior to Service Pack 3. Installer writers who want to have an installer that works on Windows NT prior to version 6.1 will use the locale API, because that's what exists and what works.
It's also what's right.
There's a difference between a geographic ID and a user interface language, and you're getting them exactly backwards. The location or geographic ID of a computer is where it physically is, and that's what you need to set on the "Location" tab in Control Panel. The UI language is the language that you want to see stuff shown to you in, and that's set in a combination of places elsewhere; including the locale settings that are set by the "Formats" tab in Control Panel.
It does say, at the very top of the "Location" tab, what it is for. Why do you think that setting your computer to obtain the "local information such as news and weather" for the United States, because you've told the system that you are physically located in the United States, is the right thing to do when you are physically located in Germany? Locate your machine where it physically is, and set the language and locale to the language and currency/number/date formatting that you want to see on the user interface.
In short: Nearly 100% of the programs from different vendors aren't operating as you think. It's your thinking that's wrong, not the programs.
Best Answer
On Windows 8 hit Win+W and type in the search
Region, click on the Region and go to the Administrative Tab and click on the copy settings and make the languages changes system wide.