I use Windows Media Player rather than the Sony transfer software and find it works fine.  The way that I do it is to plug the USB lead into the 639, plug it into the computer and  the computer then pings to indicate that something is connected to it.  The first time this is done, the computer loads drivers up and then the walkman appears in Windows Explorer as a disk drive in the Computer directory tree.  If I then open WMP, the Walkman appears in the list with Music, Video, Picture etc and in its own pane in the WMP window.  From there, I can organise, synch, drag & drop etc.

Have you looked at Windows Explorer & Windows Media Player?