You can ignore the message for English (India). The "limited support"
message is relevant for Indic/Brahmic languages such as Hindi or Gujarati,
but it is much less relevant for English. If you can type English characters
and the spellchecking feature works correctly in Word, then you have full
support.
Basically, the "limited support" message in the Office Language Settings
tool dialog appears if:
1. The keyboard layout for that language is not installed in Windows OR
2. The Office proofing tools for that language are not installed.
You can see the list of installed keyboard languages in the second or third
tab in the "Regional and Language Options" dialog in the Windows Control
Panel. The English (India) keyboard layout is not available in Windows XP.
Later versions of Windows should have it.
Actually, I have to apologize personally for the "limited support" message.
I was heavily involved in designing that part of Office 2007. In retrospect,
"limited support" isn't explained well in the user interface. Also, the
message appears in cases like this, where the worst case scenario is that
Office might not recognize words like "tiffin" or "votebank."
On the plus side, the language settings dialog in Office 2010 is much
clearer. "Limited support" works the same way, but the explanation is much
better.
--Todd