I have just spend several hours getting twisted working with python 64 on my Windows 7 64 bit install so I could make a dummy test server. Basically it turned out that the 64 bit version of python posed the hindering, and i ended up installing the standard 32 bit version and using easy_install to install twisted which is now functioning.
My first thought was simply installing python and using twisted own windows install file, however this did not work at all (I have not tested this method with the 32 bit version of python, but I am guessing it would work as supposed).
Next I tried to use easy_install, but I could not install easy_install from setuptools, and got a warning about python 2.6 not being installed. But when I removed the 64 bit version and installed the 32 bit version it installed without any problems. So my advice is: Use the standard 32 bit version!
Hopefully this will be helpful to others in similar situations.