Apple makes a lot of money with iTunes on windows machines, and the Cocoa framework does not exist on Windows machines. From Apples point of view, a pure Cocoa GUI for iTunes would be a disaster, until Microsoft provides some compatibility layer, which i cannot see in the current Windows 7 versions.
The main Carbon frameworks are integrated in the CoreServices framework, which is a 64-Bit framework. All sub-frameworks are 64-Bit, so Carbon and 64-Bit do not exclude each other. Just the "Carbon.framework", which has nothing to do with the CoreServices sub-frameworks is a 32-Bit framework.
Apple appear to be gradually making an application layer for windows again (or maintaining the old one at least), check out your C:\Program Files\Common Files\Apple\Application Support directory...