Can I back up an iphone without syncing my current library?

I need more memory space on my itouch (8GB). My brother has a 16GB iphone 3g that I want to use for my music and apps. If I backup the phone, it starts syncing.

Where does the iphone backup to on windows 7?
Will my itunes library be lost when it syncs on the iphone?

My goal is to sync my library to the iphone, but first backup the iphone.

(sorry, really repetitive)

Sure you can do that. Syncing won't do anything to your library. It will also backup. Don't worry just press back up. Right click Ipod and press back up. Hope I helped and thanks.

Don't sync it, just click backup… And make sure you have updated both the ipod/iphone and your itunes to the latest version then you can sync it…
hope i helped ty.