Be careful. iTunes won't backup any music, photos or videos. All you can sync to your computer is the content of the camera roll (it contains the photos you took yourself, pictures you saved from other applications, the Internet etc). But: music, movies and photo libraries (from iPhoto etc) your friend copied to the phone at some point will not be synced to your computer. It works sort of one way only...the best would be that your friend syncs the iPhone to the computer they used to get all the music and stuff onto the phone in the first place.