Sorry if this is in the wrong place, i'm new here and just need a bit of help with my iphone/itunes! Basically my new iphone 4s was synced to itunes on my mac. I put my computer in for repair, and they had to replace my harddrive, and therefore wiped everything off my computer. Now, when I plug in my phone, it doesn't register that it's the same itunes. I want to re-sync it to put all my updated music and such on there, but it says that I have to erase the phone in order to do so. I don't know if this will erase everything, or just the music, photos, apps, etc. Is there a way that I can update my songs/photos and such without it wiping all my contacts and messages and stuff? I don't care if it has to delete all the songs and photos, as long as I can keep everything else.

Any help would be much appreciated

Before you attempt a sync, you should back up somewhere. given that that cant be with itunes, another solution must be found. When in doubt, I copy everything from my iphone via Phoneview. Theres a 7 day trial, I'm not sure if its crippled in any way. I bought it straight up, its perfect for times like this. Then theres iexplorer which *might* do nearly the same thing, and its free. After you copy what you need to the computer via one of those apps, let it sync and you'll be ready to start over.

Phoneview does work well for copying various data from and to the iPhone. The demo is very limited, but it does allow you to test the functionality on a few files or items. Probably a good investment ($20) for the hassle it can save.

Oh okay so basically I need to back it up with a program first, otherwise it will reset my whole phone? This is so irritating.

It would really help if Apple allowed an initial restore from iPhone for such occasions, but maybe that could get messy.

If you synced your contacts with Address Book they will be on your backup of the Mac's hdd.
That leaves only the text messages. Unfortunately you need a program like phoneview to backup and restore those.