New OS install, new iphone, iTunes SYNC ISSUES!!!!

For the love of....

I've had to reinstall my OS and also have a new iPhone. Of course, iTunes is severely confused now and wants to erase data from my iPhone---sorry, I mean 'sync' my iPhone. Because it surely feels that I'm trying to rip someone off by --heaven forbid-- syncing my phone with two computers. Which really aren't two computers, but simply a new OS.

Ugh.

What are the proper steps, can anyone link me to a how-to or something? I was planning to backup my phone today and of course now iTunes isn't happy with my apps, my music, my photos, will now give me 2x the notes, blah blah...

And of course Apple would like to charge me to speak to someone on the phone about this...

Help!
Thanks.


---not that it's crucial for this posting, but:
OS 10.6.8, iTunes 10.6.1, iPhone 4s iOS 5.0.1

Hi my new iPhone did this too! not to worry,BACKUP your iPhone then reset to Factory then plug back into iTunes and upload again then it recognises it,I haven't had a problem since then. when you plug your iPhone back in it will ask for a password so make sure you remember this password. Hope this helps.
iTunes Not Syncing Entire Music Library? - Switching To Mac