File this under: Experienced users only
Warning: We’re just going to say that Windows Phone 7.5 Tango is not that big of a deal. It’s a tiny update with a few MMS enhancements and some minor tweaks (most of which are undocumented, but see our hands on video to get an idea). So we’re not sure that trying to manually update your Windows Phone with Tango 8773.98 is a high priority. Nor is the risk of damaging your phone and blocking the upcoming 7.8 update.
And let's be honest, a lot of "fixes" and "tweaks" for your Windows Phone will come from the OEM firmware which this does not provide. Finally, this does not provide the new Start screen. That's Windows Phone 7.8 this is still 7.5.
Having said that, user bobzero on the XDA Forums has posted the Tango OS cab files direct from Microsoft and the needed language files to get the update started. It will break inter-op unlock (for the tiny few of you who have that) but you can go through the process again re-enable it.
The big question for many of you will be How do I do this? It’s not Android-custom ROM hard, but it does require a little prep work and some careful reading.
Luckily for you we wrote a nice little tutorial on how to manually update your phone to 8107 to get the much needed “disappearing keyboard fix”. That same process should work here so long as you replace the 8107 CAB with the 8773 one, obviously. Likewise, you’ll need the language packs too which bobzero has given you.
We haven’t done this yet ourselves but we do have our trusty Samsung Focus 2 and a bottle of Wild Turkey that says we’re going to try it soon.
As usual, sound off in comments on your experience and please, don’t blame us if you damage your phone. Remember: read, ask questions and take your time. And if you're on OS 8107 you need to go to 8112 first.
Source: XDA Forums; Thanks, bobzero for this tip and your past ones ;-)