Windows 7! Language Packs
I have written about how to download and activate officially the Windows 7 RC version from Microsoft website. Now, we have regular updates for this version. Recently, Microsoft released updates on Language packs for Windows 7 RC version. Though we could see them on several torrents before, I could see them only recently. These cannot be downloaded from Microsoft download centre, but only can be had from Windows Update which is available on Windows 7, as link in Start -> All Programs -> Windows Update.
You can check the screenshot for these updates here:
By using these language packs one can use the Windows 7 interface in their own language. Unfortunately, I could not find any Indian language in there. Also these updates are available as optional updates. If you want to use several languages on the same Windows 7 version, you just need to create different user accounts. Then each user account, can be customized for a different language.
You can have further details from this Microsoft support article.