Is iTunes for Windows affected by the code responsible for the goto fail vulnerability?
The "goto fail" bug was part of a OS X library that checked that a valid SSL certificate also matched the host records it was exchanging traffic with.

Since many applications use SSL first identify a web site securely and then encrypt the traffic, having the library in the core OS lets each program not have to do the work to validate a cert. By patching/fixing this library the problem is solved for all applications that relied on that fucntion.

On OS X, iTuned relied on the system to validate SSL certs and thus didn't need a patch. There isn't a published vulnerability listed (yet) for iTunes for Windows, so you should be in the clear for that one issue. 

Of course iTunes could have other security issues that aren't published or patched yet, but there's not any evidence that Windows iTunes is vulnerable today to the same code problem.