My situation seems to be very specific and I can't find an answer yet that helps.
When I got my iPhone 3G a few years ago, I was sharing a laptop with my boyfriend and synced it on iTunes on his computer. During that time, the phone was damaged, but I was able to back it up and restore everything onto the new 3G.
A few months ago I got my own laptop. I've been "backing up" whenever I connect my iPhone to my new laptop, although nothing shows up in iTunes to indicate to me that any data has transferred. I've just "transferred purchases" and those are showing up, but not my playlists. I'm aware that I can't sync music and app libraries between two computers, so I haven't synced anything from the new computer because it will wipe everything on the phone. This is obviously irritating for both of us, since I've had to use his computer any time I want to change something, and also because I can't add the new music I've downloaded on my new laptop.
I have just finally upgraded to an iPhone 4S. I want to back up everything from my 3G and restore onto my 4S, but I would like to do it on my own computer. I don't mind losing the music anymore that had been on his computer (it was all from CDs that I can upload again, the rest is all purchases that will transfer.) What I am worried about is all of the other data. As I said, I have "backed up" my current 3G, but there has been no indication that anything from it has actually transferred to my new computer (also it does it suspiciously quickly.) How can I check that everything will transfer? Or will I have to just do it all from his computer? I'm worried that if I have to "sync" my old phone to my new computer before I can properly back it up, that it will delete important data that isn't on the new computer.
Also, if I "restore" everything from the 3G to 4S, will it also save the "sync" setting, or can I change it to "manual" (which I would have done in the first place if I'd known it would have cause all this fuss.)
Thanks in advance for any help.
You can open iTunes and go Preferences, on the Devices tab your backups will be listed if you have any. Another way to confirm that you backup is there is to go to \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\, which is the location of the backup(s). If this is empty you don't have a backup on this computer. To prevent inadvertent (automatic) syncing when you connect your phone go back to iTunes>Preferences>Devices and check "Prevent...from syncing automatically". Then you can connect your phone and it won't sync unless you click the Sync button. Finally, sync settings aren't stored on the phone (and thus not in the backup). Your sync settings will be whatever you set them to be in iTunes.
Here's a guide on transferring information to a new iPhone: http://support.apple.com/kb/HT2109.