You can't convert an USB 1.1 port into a USB 2.0 . But you can buy a USB 2.0 expansion card and install it in one of your computer's available PCI slots.

USB 2.0 cards range in price from $15-100. In most cases, a cheaper one will perform just as well as the expensive ones.

In most cases, you could leave things like your USB mouse, printer on the older USB 1.1 ports and put devices that need high transfer rates on the ports in the USB 2.0 card.

You can buy a USB 2.0 PC card from here.