It could be your mom's computer. If you have another computer in your house, try using them on the other computer. If you don't, test them on an MP3 player pr a friend's computer. If your headphones work on other devices, you know it's just your mom's laptop. If they don't work on other devices, it's the headphones that aren't working properly. (But them again, if you aren't sure, ask the people at the store you bought them from. I don't know if the headphones could be MP3 only, or something.)
If they aren't working, you should just bring them back to the store you bought them, and ask for a refund or ask them to get you another set of headphones. It's probably just a deflective set. If you get another pair of headphones and they still don't work, return them and get a refund, then buy another model from a different brand.