My friend accidently bought Japanese MS SQL Server 2008 R2 instead of the English version.
However, we currently have English Windows Server 2008 R2. Can we install it anyways?
I don't have a test machine to try it out on first to see what happens.
If you have another installer for the English version the keys are probably the same. The important thing is that you have a license.
Even if you can install it, how do you expect to use it? If the server's that important, do you really want to be administering in a foreign language?
The obvious question is, what language do you want it to be in?
Assuming English...
Best thing to do is have your friend contact who sold him the copy and raise all manner of demons in an attempt to either get your money back or get an English copy. No sense in trying to deal with it in a language you do not want.
According to the documentation it is supported:
Local Language Versions in SQL Server
http://msdn.microsoft.com/en-us/library/ee210665.aspx
The English-language version of SQL Server is supported on all localized versions of operating systems.
Localized versions of SQL Server are supported on localized operating systems with the corresponding language or on English-language versions of supported operating systems by using the Windows Multilingual User Interface Pack (MUI) settings. For more information, see How to: Change Operating System Settings to Support Localized Versions.
Localized versions of SQL Server can only be upgraded to localized versions of the same language, and cannot be upgraded to the English-language version.
Localized versions of SQL Server can also be installed side by side with English-language instances of SQL Server.
SQL Server 2008 R2: How to: Change Operating System Settings to Support Localized Versions
http://msdn.microsoft.com/en-us/library/ms144258.aspx
Localized versions of SQL Server are supported on English-language versions of supported operating systems through the use of Windows Multilingual User Interface Pack (MUI) settings.
However, you must verify certain operating system settings before installing a localized version of SQL Server on a server that is running an English-language operating system with a non-English MUI setting. You need to verify that the following operating system settings match the language of the localized SQL Server to be installed:
The operating system user interface setting
The operating system user locale setting
The system locale setting
If the settings do not match the language of the localized SQL Server to be installed, then use the following procedures to correctly set these operating system settings.
To change the operating system user interface setting
If not already installed, install the operating system MUI that matches your localized version of SQL Server.
In Control Panel, open Regional and Language Options.
On the Languages tab, for Language used in menus and dialogs, select a value from the list.
This setting will affect the user interface language of SQL Server, so it must match your localized version of SQL Server.
Click Apply to confirm the change, and OK to close the window.
To change the operating system user locale setting
If not already installed, install the operating system MUI that matches your localized version of SQL Server.
In Control Panel, open Regional and Language Options.
On the Regional Options tab, for Select an item to match its preferences, select a value from the list.
This setting will affect culture-specific data formatting.
To change the system locale setting
If not already installed, install the operating system MUI that matches your localized version of SQL Server.
In Control Panel, open Regional and Language Options.
On the Advanced tab, for Select a language to match the language version of the non-Unicode programs you want to use, select a value from the list.
This setting will allow SQL Server Setup to choose the best default collation for your SQL Server installation.