Free licenses of some sort (update: Windows 7 Professional license)
MSDN Academic Alliance is a program Microsoft offers to colleges and high schools to provide their students with access to popular design and development software, along with other products such as Windows. If you attend college or high school, talk to the appropriate highers-up about getting access to MSDN AA to take advantage of it. MSDN AA has historically provided professional/business-style versions of Windows for students;