HELPROOM ANSWER Mobile (3G) broadband isn't only useful for getting online on the move, it can also be used with any PC in range of the operator's phone mast. A dongle is ideal for use as a backup on a home PC if your broadband connection is flaky, or if you'd simply prefer not to sign up to a lengthy contract.
You shouldn't need any extra hardware. Simply plug the dongle into a USB port and let Windows install the software contained on the device. This will also be available at the operator's website, provided that you have another means of getting online.