MSDN Academic Alliance is special MSDN subscription package for students. With MSDN AA they can download all Microsoft’s software that they need for their studies and for private use, and everything is free. For example, they can download Visual Studio 2008, Windows Server 2008 Standard and Enterprise, Windows XP, Windows Vista, Office Visio… Commercial use of these programs is forbidden. Downloads goes thru e-academy ELMS (e-academy License Management System). Dimitris-Ilias Gkanatsios has just informed me that Windows 7 Professional is also on this list, so if you are student who has MSDN AA account, you can download Windows 7 Professional for free at e-Academy.
IMPORTANT! Your ELMS administrator needs to approve Windows 7 so you can be able to download it! If Windows 7 is still not on the list (it is not on the mine yet, also), wait for some time till final approval.