Use Media Access Control (MAC) address filtering. This is an individual and different 48 bit hardware identifying number built into every single piece of network equipment. Under Windows, running either ipconfig /all (command line) or winipcfg (Windows utility) will tell you the physical address. Don't forget you may have multiple adaptors, so check you have the right one showing. A hacker can sniff the MAC address and fake it, but it does raise the level of complexity of an attack.