Vista introduces a big change from previous windows OSes, that is the MUI (Multilanguage User Interface) is deployed and used by all Vista components. Therefore, it is possible to change the display language of the Vista OS itself without having to patch resource files and some other dangerous things, just install the target language MUI and let the Vista use it.

However, it is a sad news that the ability to switch between MUI is only available for Vista Enterprise and Ultimate editions. For other editions (Home basic, Home Premium and Business) only one MUI can be installed and the other MUIs is reported to be deleted after installation. Mine even did not ask for language to be installed at all.

Now I have a new PC came pre-installed with Japanese Vista Home Premium. It is no problem for me to read Japanese at all, but my wife prefers English to Japanese. Moreover, the Vista Media Center looks awful with Japanese menu. With the Vista putting its localized resources on MUIs, there must be a simple way to safely trick Vista to use another MUI, so I started googling for success stories of installing other MUIs on Vista Home Premium.

Well, the answer to my searches is, as I expected, it is possible by :

• Download MUI pack in executable (.exe) form of your target language. In my case I downloaded the en-US pack.
• Execute the executable. It will create lp.cab file, but will soon erase it and abort the installation when it finds out that it is not running on Vista Enterprise or Ultimate so rename the file to prevent it from being deleted.
• Extract the lp.cab file. You will find a lot of .manifest files and directories full of .mui files. These are the MUI files.

Now the question is, how to install these files. There are a lot of them. Thousands.

For the first try, I copied MUI files which are also available in your original language directories (mine ja-JP) to windows\en-US, windows\system32\en-US and program files directory.

Oh, and since Vista Home Premium only allows one language, I also changed the main language in registry by renaming:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\ja-JP

to read

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\en-US

and created a string value inside it :

DefaultFallback = "ja-JP"

Then changed the value of strings in it :

LCID = 1033 (0x409)
Type = 145 (0x91)

After that I rebooted the system and viola ... the Vista now displays everything in English instead of Japanese!

That simple ? Well, not. It soon appeared that just blatantly copying MUI files to windows\en-US, windows\system32\en-US, and program files did not cleanly change the display language to English.

After some quick checks, I found out that:

• Help system does not work. The help window just crashed and refused to start.
• Windows defender can not be started.
• Windows update window is blank with one or two icons and it is disabled.
• Windows sidebar does not open gadget browser when "add gadget" is selected (clicking the plus button or starting from context menu)
• When log on, Vista reported that it failed to connect to the Event Notification Service and that this prevents normal users (non-administrators) from logging on.

Other than those, everything is fine (well... maybe).

Note that I can always revert back to Japanese anytime by deleting:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\en-US

and restoring:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\ja-JP

and reboot.