Does a license key for Windows 7 Pro (PT-PT) from MSDN-AA work on Windows 7 Pro (EN)? Is this valid and legal?
Or do I need to use it in PT-PT?
This is legal and downloaded from MSDN-AA program. As said "The MSDN Academic Alliance is the easiest and most inexpensive way for academic departments to make the latest Microsoft software available in labs, classrooms, and on student PCs."
My question is if a MSDN-AA key works on different language or is language-dependent.
In my experience working as a helpdesk tech, Windows license keys are not location specific, let alone language specific. However, you can only switch display languages on an in-place install of Windows 7 Ultimate or Enterprise. I can't guarantee this, but I don't believe that your Portugese install disk will have the English language pack included, so you will probably be unable to switch the language via a reinstall.
In this case, you would have only two options: upgrade (in-place or not) to Windows 7 Ultimate, or purchase an English copy of Windows 7. Either way will incur the cost of a new license.
The license key will work just fine with Windows in any language. Unfortunately, for reasons that mystify me, they have decided that Language Interface Packs (LIPs), which used to make it fast and easy to switch the interface language, will now be a feature only of Ultimate and Enterprise editions. That said, you can still select whatever language you want at install time. The Portugese install disc provided my MSDN-AA should still have English as an option at install-time, if not you can use the license key with an English windows install disk separately with no problem, as long as it's the same edition of Windows. This page lists official sources of ISO downloads, including the English version (I have no qualms about linking to this list, because the downloads are of unmodified retail Windows discs and do not contain activation hacks/illegitimate oemact/etc., they are intended for use with a real Windows license).
License keys are only specific to the edition (Home/Professional/Ultimate). Language and architecture (32-bit vs. 64-bit) do not affect the validity of a license key. You can use your Windows 7 license key in any language variant from MSDNAA and legally install any language of Windows 7.
MSDNAA sometimes will provide language packs for download even if you are not provided with an install disk for every language option. If you want to change the language after the fact, log in to MSDNAA, and look in the software list for Windows 7 Language Pack - DVD (Multilanguage). This will download an ISO containing all of the language packs. Windows 7 Professional, which is the version provided by MSDNAA, does not have built-in support for switching the installed language pack; only Enterprise and Ultimate have this feature. However, you can use third-party tool Vistalizator to change the installed language pack. I have used this tool before, and it works well.
You could alternatively just download an ISO of Windows 7 Professional EN. See Where can I download Windows 7 (legally from Microsoft)? for download links.
Whatever party you purchased from should have conveyed to you a valid license key.
EDIT: Looking at your comment above , yes, you should be fine. I've done this with russian>eng before and it worked so I figure pt should be the same.
