I've been traveling quite a bit lately and the one question I've gotten a lot in Asia and in Europe is around Language Support in Windows Mobile so I thought I'd attempt to address it. 

Unlike Windows Vista, Windows Mobile doesn't have a MUI or Multilingual User Interface on a single image that supports double bit characters (Chinese/Japanese) unless you get a device in a region that uses that double bit language.

The question that I get most often is, assuming I use an English language version of the operating system.

1. Can I input in a double bit based language like Chinese or Japanese?
2. Can the system display and send and receive messages written in a double bit language?
3. Can I change the regional settings to support another language?

Since the Standard and Professional versions of the OS differ I've covered their multi language support independency.

Windows Mobile Standard/Smartphone (Non Touch Screen)

1. Inputting in a double bit based language like Chinese or Japanese - Unfortunately you cannot without a 3rd party add-on like CEStar
2. Reading double bit based language like Chinese or Japanese - Unfortunately you cannot without a 3rd party add-on like CEStar
3. Changing the regional settings to support another language - Here we do have an answer, on Windows Mobile Standard devices you can go to Start -> Settings -> Regional Settings -> and Choose Language - The number of languages listed here will differ on different phones and won't include double bit character languages in general.

Windows Mobile Professional (Touch Screen)

1. Inputting in a double bit based language like Chinese or Japanese - Unfortunately you cannot without a 3rd party add-on like CEStar
2. Reading double bit based language like Chinese or Japanese - Unfortunately you cannot without a 3rd party add-on like CEStar
3. Changing the regional settings to support another language - Windows Mobile Professional device do have a regional Setting menu that lets your choose the Region.  It is located under Start -> Settings -> System -> Regional Settings.  Here you can choose a supported language but you will find that Chinese and Japanese are not on the list. In addition, a few have a custom rom image prompt when you hard reset the device, that asks you for the location and then installs regional language packs.

Solutions:

If you are looking for a phone to support English and double bit characters you have 2 choices. 

1. You can purchase a regionalized phone.  They will come with the local language and English.   This can be difficult if you aren't in the region however companies like Expansys can get you a regionalized device wherever you live.
2. Purchase a 3rd party add ons like CEStar that will add the language support you need.