5 years? Sounds about right, that's when most laptop batteries completely wear out and die. You'll have to replace your battery.
Some tips on increasing battery longevity:
1. If you are on AC power all the time, discharge your laptop battery to about 50-60% and take it out of the laptop and store it somewhere safe.
2. If you absolutely want to keep your battery alive for a LONG time, put your battery in a cold environment like a fridge. Just make sure you leave the battery out for several hours if you do leave it in your fridge (when you want to use your battery), so condensation has a time to escape into the air.