Mirror is extremely small in size (88Kb) and requires no formal installation. As it back-up file using multi threading, it requires only a few system resources; only files and folders are copied, so disk writes are held to a minimum with the result being a much faster backup compared to traditional methods.
Using this utility is very simple. Run the tool and select a target location (destination folder), then select source folder (the folder and its contents to mirror). If you select Synchronize Target, items not found in the source folder will be deleted in the target folder. After configuring the tool, minimize it to system tray, it will back-up anything from the source folder.
As mentioned, the program is free and clean (check it here) and works with all versions of Windows.