Ipod issues (Apple iPod Nano (third generation, 8GB, pink))



i was wondering if anybody could help me. my sister recieved a 8gb ipod nano for christmas and she is having problems with sending music and video over to it. everytime she sends something over to it using itunes, it some how deletes everything she has already put on. could this be a hardware fault or something we have done wrong on itunes:confused:. i would be extremely greatful if someone could help me solve this problem. thanks in advance:)