Did you test speakers or another headset?
Did you install the audio drivers for your MB? Check in Device Manger (Sound, Video and Game controllers) to make sure the audio chipset is installed.
Is the Speaker settings in the toolbar set to zero or mute?
Ok, First I'll say only use Worst Buy as an absolute last resort, unless you personally know the person working on your PC and you get somekind of discount because the are exteamly overpiced. There is no telling how expierenced the person working on your computer is, and from my personal encounters with them, at least at the stores around me, they shouldnt be allowed to touch a PC.
Now to your issue you are having, lets start from a simple begining and work up from there.
----VERY FIRST THING TO CHECK---- Look at the pictures below and make sure your plugging them into the GREEN port.
1. Check the Headset with another PC or a MP3/CD player.
2. All your volume settings in windows are turned up and not on mute.
3. Do you have a sound card? or are you plugging it into the back of your motherboard? We will worry about the front panel audio later.
4. If you have a soundcard make sure thats what you are pluggin them into and update the drivers just to be safe. If your plugging them into your motherboard, updae your sound drives for the board.