When i plug my iPhone 4S into my Windows laptop, it won't connect to my laptop or iTunes, how do i fix this program? Thanks!

Everytime i plug my iphone 4s into my windows laptop, usually it comes up with a small box saying 'installing device' but now it comes up with a box saying 'usb device not recoginised'. i have 4 usb ports in my laptop and i have tried plugging my iphone into each one, but it comes up with the same message. After a while it will charge my phone and connect to my laptop but it wont connect to itunes.

Are there any solutions to my problem which doesnt include me deleting itunes because i dont want to loose my music.

Thanks