W2k File Syncing

Greetings!

I have 4 computers, all on my LAN, running W2Kpro.

I maintain a music library (all wav files) that is currently updated only on an ext hdd attached to one of the computers. All subdirectories of the main music directory exist on all the other computers, including the hdd on the host machine to the ext hdd.

What program (preferably freeware) will check the ext hdd and sync the changes and content of its directories to the directories on all my other machines, or ones I designate, on the LAN?

Hope this question is posted in the right area and this makes sense.

Thanks for your help!