Computer Question

Here's a computer question that seems so simple that I can't believe I can't solve it or find a solution online. This applies to computers running Windows XP.

Moe, Larry and Curly each have a computer and all three computers are networked. Each uses the others' computers from time to time. Each has an account on each computer so Moe, for instance, can log into the Moe account on any of the three computers and work. What they want to do is to keep their Documents Folders in sync. Moe would like to be able to click one command on his Desktop and have all three computers automatically sync themselves up. The trouble is that no program seems to want to sync up files that are in three separate Documents and Settings folders.

There must be a simple way to handle this. What is it?