What should I do if my Xbox 360 is scratching my games?

My warranty for my xbox 360 is over and I have already had it fixed for the RROD, but since it has been "fixed" my games have been freezing up or saying disc is unreadable. What I notice when this occurs is that the system starts to make an almost grinding sound and then the error message occurs, or it just freezes. I looked at the discs that have been freezing and see many scratches all over them but I take good care of them putting them in their case every time. Xbox customer support has been little help and I don't think I should pay microsoft $90 to get it fixed when its not a guarantee that it would not break again. Any other suggestions?