The Student Edition is ONLY available in 32bit. It will run fine on a 64bit OS. We took the decision to make it as easy as possible for Students to obtain and use Solid Edge. The Solid Edge University Edition is available in both 32 and 64 bit and schools, colleges, and universitiy customers using the University Edition can make it available to their students.
As Doug says, you can run 32 bit on 64 bit OS. The only reason for a 64 bit SE is if you are doing assemblies of 50,000 parts or that kind of thing. Guessing you might graduate before you have time to model enough parts to choke 32 bit SE. :-)