I don't know why, but if your iPhone has one iTunes library and your laptop has a different iTunes library, that's a conflict and it doesn't know which one you want to use. Apparently the software isn't sophisticated enough to merge the two into one big library. Before you would do anything else, I would try to back up what's on your iPhone to a CD or DVD-R, so that you don't lose that music. That may mean first copying it to your laptop's hard drive, then backing it up onto a CD. Then no matter what you do next, you won't truly lose anything. After you have done that, I would try importing all the songs from that into your iTunes on your laptop. Then your iTunes Library on your laptop should have all of your music, merged into one Library. Then you could sync your iPhone to that, and that should solve your problem without losing any of your music. Apple should address this in the future with a "merge libraries" function or something. There may be some reason why they haven't done that yet, possibly that it could make violating copyright law easier or something. But for now, I think you will have to use this manual method to get all of your music into one iTunes Library on your laptop. Then it should be simple to sync your iPhone to it.