Is there a way to pass the RAM limitation?

if my motherboard have 3 slots and it support 512 RAM max, I only use 1 stick and it full, two slots left with some extra RAM, if i put more in, the comp would go to standby mode(soemthing like that, when the light on the monitor turn yellow with a blank screen while the comp run) after the start up, so, i wonder if there's a way to get through this and pass this limition.... if it's possible and you know, please let me know, and please include the consequences ....