I have Windows 7 Ultimate RTM (7600) installed on my laptop. I installed the Turkish language pack from Windows Update but some texts like "Welcome" "Shutting Down" and "Starting Windows" are still in English, but the others are translated into Turkish correctly. Did anyone face with this problem?
Language packs are, by default, enabled on a per-user basis. Your Turkish pack is probably enabled just for your user at the moment.
(If your Control Panel is in Classic View, follow the following:)
Check the two check boxes at the bottom of the window displayed:
and reboot your system once instructed. This should apply your language pack to the system accounts and the text during boot up and welcome screen will be localized.
Some language packs are what is known as Partially Localized Language Packs. They don't contain a 100% localization of all resources, although they do contain all the resources. The non localized resources are usually in the English language. See, Understanding Language Packs
I'm unsure as to how and when do Partially Localized MUI Packs evolve into fully localized ones. Being the case Windows does get distributed in Turkey fully localized, I'm sure it is simply a matter of time until the folks at Redmond update the Turkish MUI. (Please remember: Windows 7 is still not officially out)
FYI, just a few months ago, the Portuguese Pack was also only partially localized. From what I can gather with a quick inspection I did recently, the pack I downloaded through my MSDN subscription last week is already 100% localized.