How do I fix my RYOBI 18.0V batteries?

My RYOBI batteries will not charge. When I put them in the charger, I get the yellow and green lights which indicate the batterries are shot. I've seen websites touting a method for resurrecting batteries that won't take a charge. Any way I can salvage these things or do I need to get new ones? The batteries are around 6 yrs old.