First, you should find out what you have. Second, what are you plugging your headphones into? Do speakers work? It may be as simple as getting the right drivers, or just switching to the correct audio out device in Windows.
If the speakers work plugged into the back, and the headphones don't work plugged into the front, either the front IO isn't plugged in, or you have to change the active jack to the front using the Realtek software, or both.