Why can't I transfer anything from my PC to my Iphone?

I just bought a Iphone 4s. I can't transfer anything from my pc to my Iphone. Not a pic, not a ringtone, not music, not anything. Also everytime I sync my phone, I get this message saying that files could not be transferred ti your Itunes library because you are not authorized for them on this computer. My computer is aurthorized(I have authorized and deauthorized it to try to reset, but same result)

this is really frustrating and I am about to cash in on my 14 return . any ideas?