i have an iphone 3g, version 3.1.2 which i use here in naija. I recently transfered some music and from my computer to my itunes and i tried to synchronise with my iphone. It says that i was already synchronised to anothe library (? applications) and that i could only synchronise to one library at the same time. i dont want to do system backup  and  system restore as i am afraid of that cos i may loose my paid appilications. How do i get my media to my iphone .Thanks

well it seems that you already have media or info from another pc synced to your iphone. in order to sync to your new pc without losing your info you will have to download a software on cydia called swaptunes. what this does is it allows you to sync two libraries to your iphone at the same time.

check it on cydia, download /install it and enjoy! i have had it on my iphone for a while and love it.

Here comes a good news! We can backup any data on iPhone/iPad/iPod to iTunes, Computer and Back in a simple way!
With iPhone Data Transfer software, you can transfer videos, music, photos, playlists, contacts and more from your iPhone, iPad and iPod as easy as pie.

If you lost data of your iTunes library, replaced your computer or even re-installed OS and forgot to back up your iTunes library, you might have lost your media on iTunes. Even if you try to sync with your iTunes account from your iDevice, it will almost surely be wiped out.
how to transfer music from iPhone to computer
Okey, all you need is iPhone Data Transfer program to restore everything in your iTunes library with ease.
If you want to have a try, you can follow the steps.
how to transfer music from iTunes to iPhone