You can install 55 Vista LIP languages on top of specific MUI languages
Compatible with Vista Service Pack 1 and Vista Service Pack 2
User Account Control (UAC) compliant - prompts for administrative privileges
Windows Speech Recognition works with all supported languages:
Chinese, English, French, German, Japanese and Spanish
Languages can be installed either in Internal or in Express mode, see details Multiple languages in Windows
To be able to use different/multiple MUI display languages:
You are the lucky user of Windows Ultimate/Enterprise
Upgrade your edition to Ultimate - purchase a Windows Anytime Upgrade
Get a Windows installation DVD in different language and do a clean install of Windows
(you can use Windows Easy Transfer for all your data and settings)