I think nukemaster hit it on the head. Many Asus laptops employ a 'combo jack' that fits that description. While it saves on overhead and the trouble of soldering a separate port, it seems to be usually not a desired thing by end-users.
If it comes down to it, you may need to look into an external USB sound stick/hub. Asus, somewhat ironically, makes a very well received one: Asus Xonar U3.