usb 2.0 ports

i have a wireless modem the uses a usb port and sometimes i get a message saying that my computer doesnt have highspeed usb ports (2.0 im presuming) and that the modem is made for them therefore it will cause some slow down. I was wondering if i was to buy a new usb port would i be able to install it myself and how much would it cost

 

You can add them yourself if you are not worried about opening the case.
You can get a PCI card that simply slides into an open slot on the motherboard. They are not expensive $20 or so an up depending upon the amount of ports.