Robocopy is already included in Win7, but you need to know command line.
http://ss64.com/nt/robocopy.html

Otherwise, there are lots of sync apps out there.
http://synchronicity.sourceforge.net/
http://sourceforge.net/projects/freefilesync/
http://www.microsoft.com/en-us/downl...ng=en&id=15155
http://synkron.sourceforge.net/about.html