USB connection problem......!!!?

on my mother board it says usb2.0 but the actual speed is 1.1 i brought this pc from ebay as a custom build pc and of course since i dont know how to fix it i just simply brought a usb port added to it and at first it 1.1 as well then some how i got it to work and now i just reinstall the pc and cant get to work hlp plz