File Synchronizer is a free program that lets you synchronize your folders easily in Windows 7 & Vista.
If you have a folder with plenty of sub-folders and files and if you want to sync it with another folder, maybe even on another drive or an external media, then this freeware will scan both the folders and tell you whats missing where, allowing you to sync the.
It is great for synchronizing large collections of media files such as MP3s, Videos, etc without copying every file. It saves your time by only copying the files that are new or different.
You can also use the Clone Mode to synchronize a folder to match a master folder.