program for backing up data

["Nirmal Govind" <nirmalg@psu.edu>]

Hi.. is there a free program for backing up specific folders on the hard disk
onto a CD or external hard disk? I mean something that doesn't overwrite files
that haven't changed etc. and only makes the necessary
addition/deletion/replacement... would be even better if there was something
that creates a compressed image or something and writes that to the CD if the
total size of data to be backed up is greater than 650 or 700MB..

Please cc me on the reply..

Thanks,
nirmal