Just like SQL Server 2008, you can install SQL Server 2008 R2 on a MUI system. Additional checks have been added to SQL Server 2008 R2 to ensure you don’t install on an unsupported localized or MUI system. Therefore it is important you properly configure your system prior to the installation.
Here is the official documentation on the SQL Server language support: http://msdn.microsoft.com/en-us/library/ee210665(SQL.105).aspx.
Below, I have the instructions on enabling MUI on a Windows 7 system but should be similar for other operating systems.
1. Open up “Region and Language” and choose Japanese.
2. Change System Locale on the Administrative Tab by clicking on “Change system local…”
3. Select the Current System Locale:
4. Click on “Install/Uninstall languages…” to install the language pack.
5. Go through the wizard and install the language pack
6. Now run the localized version of SQL Server. If you immediately see a message indicating the language is not supported, ensure the language that you are trying to install matches the MUI language and the setting above are correct.