Nikon D5000 battery won't charge

When I want to charge it, the light flashes, but the battery won't charge.

When your Nikon has been charged for about 1 hour, you can touch the the battery to see whether the battery is hot. If the battery is hot, it means that the battery is charged, but it is broken. So you should go to buy a new battery.
If the batttery is cool. It means that your battery is not charged. Just some problems with the NIKon D5000. You can use an extenal to charge the batery. I think you problem will be sovled.

if you want to get more information please vist the below website

One of two things. The battery or the charger is toast. What's the age of the battery? These things don't last for ever. Also the charger could be bad.

I'd order another set - both from Nikon or from another site that sells Nikon batteries and chargers.
But, you must buy both. These things are specific to each other. A mismatch can cause over heating even fire… So buy them together - the ones designed for each other.