SyncToy to synchronize your files

A while ago I started to use SyncToy and I'm very happy with it. It's free from Microsoft and available at here.
White paper for SyncToy.
Overview
Increasingly, computer users are using different folders, drives, and even different computers (such as a laptop and a desktop) to store and retrieve files. There are new sources of files coming from every direction: digital cameras, e-mail, cell phones, portable media players, camcorders, PDAs, and laptops. Yet managing hundreds or thousands of files is still largely a manual operation. In some cases it is necessary to move files from one place to another; in other cases there is a need to keep two storage locations exactly in sync. Some users manage files manually, dragging and dropping from one place to another and keeping a mental card catalog in their heads. Others use one or more applications of one sort or another to provide this functionality for them.
Now there is an easier way. SyncToy is a free PowerToy for Microsoft Windows XP that provides an easy to use, highly customizable program to help copy, move, and synchronize different directories. Most common operations can be performed with just a few clicks of the mouse, and additional customization is available without adding complexity. SyncToy can manage multiple sets of directories at the same time; it can combine files from two folders in one case, and mimic renames and deletes in another. Unlike other applications, SyncToy keeps track of renames to files and will make sure those changes get carried over to the synchronized folder.