You can't sync your iOS device to the iTunes library if it is synced to another, meaning you have to "erase and sync" which most users do not want to do, including me.
If you need to sync without erasing, I recommend "CopyTrans". It's pathetic that Apple hasn't allowed us to do what CopyTrans is capable of.
If you need to sync without erasing, I recommend "CopyTrans". It's pathetic that Apple hasn't allowed us to do what CopyTrans is capable of.