[Samba] help

[Amani Makala]

hi!
i need to configure a linux backup server, but am not very well on the way
to configure it, let me give u some hints on the environment, i have three
windows machine and one linux machine. now i need to configure the linux
machine to be a backup server, files to be  backed up are all found in these
three windows machines, and i need to make a backup on an external hard
drive, please let me know how to do this.
thanks!