I too woould look at rsync. Most of the ports for windows seem to require cygwin, although a native port is in alpha stage on SourceForge. There is a mod to help called File::Rsync, I haven't tried it but it seems straight forward. Perhaps some other monks will have experience with it.
You could also try Unison. It has ports for windows already, which I have used for syncing backups across a network. And best of all, it's GPL.