Directory Synchronization tool

We have same directory structure(same files and directories) on various windows computer at different location. All of these compters are connectd through high speed network. People at different locations access and change the documents at different points of time in the day. I want a software to automate the synchronization of these directories at different locations. The tool should run without any manual intervention and at off-beat hours, when n/w utilization is low. Real time polling of documents is ruled out. For complex scenarios like modifcation in same file at different locations, which cannot be automated, a report should be generated detailing the same. Open to suggestions about technology, though Java is my preference. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Java, Windows XP,NT,2000