Dell Vostro 1500 Screen goes dim

For some reason, I can't view the "replies" to the posts of others who are having the same problem as me. My screen starting getter darker and so I kept raising the brightness. Last week, the screen cuts out (goes dim) when I raise the brightness even 1 notch.  Today, I can't use the charger without the screen going dim (I can still faintly see the icons thru the darkness). This seems like a backlight issue. While running on battery, the screen is dark and hardly readable. What can I do? Replace the screen, the inverter?

Thanks!