dollarlayerI would check to see if your computer even supports a mic/headphones in a single jack. I've not seen a computer with just a single jack before, but maybe that's something new they are doing?. All the laptops I've seen have 2-3 jacks.
Combo jacks are getting more and more common on laptops due to Applerexia nervosa. Just look at a lot of the ultrabooks by Asus, Lenovo, Toshiba or Dell. Apple has even patented a 3.5mm jack which has the top cut off(so it's sort of a D-shape) to ensure the audio jack isn't going to be limiting the thinness of their mobile devices any time soon.
@OP These same splitters also exist in a USB form, where you just plug a little block into a USB port and it then has headphone and microphone 3.5 female ports.