Return a new trailblazer?

Just bought a 2003 trailblazer lt. when the back window is down, it creates a head-banging vibration. practically unbearable. i've had it 2 days. I just don't think this vehicle is right for my family. Does anybody know if there's a return policy on new vehicles? As in, could I return it for my money back?

Do you have the front windows up? If you do you are causing your problem!! Try opening the front windows and see if it does the same thing!! Usually most dealers allow you 3 days to bring it back, but why do you want rid of it? Are you in buyers remorse?