I am assuming you have recently updated what version of windows you are using.
So I have some questions.
"I cannot sync it anymore" does not help us know what the issue is you are having. Whats going on? is it giving you an error? (if so, what error) does it say its syncing but then fails? is itunes even recognizing your device?
please be more specific.
I am using windows xp sp3 and there is no error message , but the problem is I annoy sync it and even the music or the videos I cannot also add it to my phone , plus the iTunes is up to date and also the IOS ..as I know that iPhone u can sync it only on one computer by one I tunes only, if yes so what should I do ?
....thanx for helping me