DreamSpark is actually now available in 135 countries, with thousands of colleges, schools and universities signed up for it. This extends to up to 170 million students worldwide, to cut down on their upgrading to Windows 7 costs.
Windows 7's equivalent is Windows Server 2008 R2, but the problem here is that it only runs as a x64 operating system. Though many x64 processors are available on the market, if you have an older machine then it may not be x64; it will be x86. You can run an x86 operating system on an x86 or x64 processor, but you cannot run an x64 operating system on an x86 processor.
The two are identical in theme, user interface, programs and applications and usage. The only exception is that Windows Server is designed for the enterprise, but it's free for students. So why not 'convert' it instead of paying through your ears for a legitimate copy of Windows?