Call your manufacturer. Some of the first USB systems came with all the proper internal hardware but no ports, while others were designed before the specifications were finalized. If you're having a problem with your USB system, ask your manufacturer if it was designed before the final USB specifications were completed, and if your USB system has no ports, ask if you can be sent an updated model. Add a second USB hub. The two rectangular connectors found at the rear of your PC are known as the root hub.
Dedicated hubs come with clusters of two, four, or more additional sockets.
Once you've experienced the ease of plugging and unplugging USB devices from a hub on your desktop, you'll never want to deal with serial and parallel ports again. You can't simply attach devices to any port, however. USB ports deliver electricity as well as data to peripherals. Just as all devices attached to a root hub must share its 12 mbps of bandwidth, they must share a finite amount of electrical power. You need to plan your USB setup around the energy needs of your USB devices.