Hello,

successfully installed digikam 3.4 on Windows7 from here http://download.kde.org/stable/digikam/
But I cannot switch translation to another language from english. Why? Missing any translation files? Trying to switch language here: Help-> Switch the language..
After restart digikam is still in english.

It is quite likely that those Windows installers are missing parts of the translations, yes - can you please check for a share/locale folder in the directory where Digikam is installed?

it seems that all files are there. I can see a lot of different translation files.

What were the names of the folders in share/locale? Was one called "de"?

As you can see on the screenshot, the names of the folders are "ar", "be", "bg" ... "de" and so on: http://picpaste.com/pics/scr-B8B6oaPQ.1395136952.png

In the 'de' folder is there a number of *.po files?

There are many *.mo files in share/locale/de/LC_MESSAGES
No other files.

Hmm, it should be working then. I'm presuming after changing the preferred language it asks you to restart Digikam?
Also, which language is set for the system as a whole?

System language is german. Only the list of languages is translated, but not the digikam interface. Digikam restarted many times. Also selected second fallback language, but the interface is always in english.

Okay, i'm afraid i've no idea why it isn't displaying itself in the correct language unfortunately.

You may want to try sending an email to the kde-windows@kde.org list - where the KDE on Windows folks co-ordinate matters, to see if any of them have any further ideas.
I suspect some environment variable isn't set, preventing Digikam from finding the translations (although if that were the case i'd suspect it to be significantly limited functionality wise).