How to back up/ transfer the contact/phone book from the iPhone to PC safely?

One of my friend is a businessman and has a lot of contact numbers in his iPhone. So he has to back up them in his PC in case that he will lose them. But he has no idea about how to do this. Also to him, a businessman, most of the contact numbers mean money. He wonders if there is any way he can set some kind of passwords for his backup files…. Any one have any idea about how to handle these problems…..
Appreciate your early reply! He is quite anxious now, since he witnessed one of his friends suffer from the lost of the iPhone……
PS: He has a iPhone 4. The operating system of his PC is Win 7.