I Cannot Install Single Language Packs in MS Office 2010by Alan Sembera
Microsoft Office 2010 provides support for dozens of different languages ranging from Arabic to Ukrainian. To change your interface to one of the languages, you must first download and install a language pack from Microsoft and then enable it from the language settings in your Word options. If you're unsuccessful in enabling the new language from Word, the most likely cause is that you're using the wrong version of the language pack.
Language Pack Versions
It's important to start with the right version of the language pack. Language packs designed for Office 2007 or Office 2013 don't work with Office 2010. Also, when you download one of the free language interface packs, select the 32-bit version with "x86" in the filename if you use the 32-bit Office, and select the 64-bit version with "x64" in the name if you use the 64-bit Office.
Although it's unlikely, there's also a chance you can't install a language pack or other Microsoft updates because your copy of Windows isn't properly registered with Microsoft. In this case, you won't see the "Download" button when you attempt to download the language pack. To resolve this issue, visit Microsoft's Genuine Validation Tool website (link in Resources).