Dim monitor

5 years old, lamps are good for about 50 000 to 60 000 hours of life you would have to do the math based on average number of hours per week/month and see where your are, several things to check initially are inside look for blown capacitors, you can find images all over the net Google "blown capacitor image" and you will see what to look for.
Next could be inverter failure as they get old and work pretty hard. Last the ccfl lamps may be dieing of old age like the florescent lamps in buildings, they get burnt at each of the ends and have a hard time lighting up.
let me know what you find.