What is Multilingual User Interface:
Before installing MUI, first read it’s description here.
After you download correct file version for your Windows 7 installation, locate file(probably in your downloads folder), just double click on the file and wait installation to finish.When your installation is finished, just go to:”Start/Control panel/Clock, Language and Region, and again select “Region and Language”(this is if you have Control panel set to Category view), and if you have it set to large or small icons, just select “Region and Language” from list.When you open “Region and Language” window, select third tab “Keyboard and Languages”, after that from “Choose a display language” select your newly installed language and select “OK”, and confirm Logging off by clicking on it.That’s it, you are finished changing your operating system language.
Portuguese (Portugal) Multilingual User Interface:
Windows 7 64bit version
Windows 7 32bit version
Complete list of Windows 7 Multilingual User Interface packs: