In my centrally air conditioned home, we cannot cool the area adequately. I've had the filters cleaned, freon checked etc. Is there an auxiliary system that can be installed without causing major disruption and expense to help cool the area?

Is the unit new?
Did or has it worked OK before this problem?
Has anyone checked the ductwork to make sure there's no problems there?
Are all the vents open and not covered up? (supply and return)
Has the system been cleaned and serviced?(condenser and the evaporater)