My iphone 4 is synced with the macbook at home, but I want to copy my music from itunes on my pc at work without touching or loosing anything else than music

Question

...but when I connect it on my pc at work on iTunes and try to check "manually sync songs and videos" I get a window asking to "erase and sync".
But it is not very clear about what is going to be erased. What will it be erased? Only music and videos? Also Apps, emails, contacts, calendar?

Answer 1

When you connect the iPhone to sync with the new computer,  a number of things will happen. If the new computer/iTunes does not contain any music, then yes, you will receive a prompt saying this iPhone is synced to another library, and if you continue, you will lose your music. However, you risk losing a number of other things, such as apps, contacts and calendar data. When you ask about photos, any photos that you have on the iPhone that were synced from the previous computer would also be lost. You need to save the photo folder from the old laptop and transfer that to the new desktop. You also need to sync the contacts and calendar to the same supported application that you were using in the past, such as Outlook, unless you are using an outside web-based sync, such as Google. Also, when you first connect the iPhone, it will make a backup, or at least make sure that it does before you attempt to sync, or you will not have a backup of some of the other things, such as mail settings, SMS, and the contents of the Camera Roll. I would import the photos from the camera roll to the new computer before trying to do anything else in iTunes.