Hi there I previously had an iPhone 3G but had it stolen, and have replaced it today with a new iPhone 4. However I've just synced it for the first time with my iMac which has my friend's iTunes account logged on it, rather than my MacBook which has got my account on it- which is obviously a mistake as now it's asking for his iTunes password every time I try and do anything!! Is there a way to un-register it from the iMac account and re-register it with my own account? Thanks very much!!