I built my computer a few years ago, before I new about WOL. I want to get that feature now, but I don't know which part I need to get that feature. What should I get to add that functionality to my computer?
Your motherboard has to support it. If it does not, there's no way to get the feature unless you replace your motherboard. Replacing it, depending on what technology the motherboard uses (e.g. DDR2, socket 940, or AGP), may also require an upgrade to any one of your CPU, RAM, or graphics card.