I found a very good article on how to copy music from Windows to your Android phone, which you can view at:
http://www.simplehelp.net/2009/07/29/how-to-copy-music-to-your-android-phone-from-windows/
Notes:
- I have not tried the following app, but you may also want to give doubleTwist (on the Android Market) a shot if you want to sync with iTunes.