Which window?
I guess it depends how bad they are. You could take it to a windscreen expert to see if they can improve it, failing that over cost etc, buy a replacement one
I've got several scratches in my passenger side one from the winter (Getting rid of ice ) Could it be polished out?
You'l need cerium oxide and a rotary to polish the glass, not an easy task from what i've heard
http://www.amazon.co.uk/dp/B005NHQBKI/?tag=cliospnet01-21