|First of all, USB 2.0 devices SHOULD run at USB 1.1 speeds when connected to a slower port. |
That said, your only method to get USB 2.0 speeds out of your rig would be to install an add in card. Below are some examples. Newegg.com is an excellent vendor.
Before buying, check the reviews for the selected product. You also need to verify you have an available PCI slot to install the card into.