Cable modems and even dial-up modems can be used with multiple computers. Many newer cable modems can be used simultaneously, allowing two or more computers to go online at the same time. Most older dial-up modems can only be used by one computer at a time, but you may wish to connect two computers to one modem to avoid purchasing a second modem if you only use one computer at a time. This will also help you avoid the hassle of switching wires when you want to use an older modem with different computers. There are two basic options for connecting multiple computers to one modem: you can connect the computers to the modem the "old fashioned" way using wires or you can set up a wireless network.
Things You'll Need
Two-way port splitter
Wireless network receivers
Ethernet cables or phone cables
Identify the port in the back of the modem. There will be a phone jack port (for a dial-up modem) or an Ethernet port, which looks just like the phone jack port, except it's a bit wider. Remove cables from these ports by pinching the tab to the cable and pulling it out.
Place a two-way splitter in the modem port to create two ports instead of just one. For a dial-up modem, you'll want a splitter that fits in a phone jack; for a cable or DSL modem, you'll want a splitter that fits into the slightly larger Ethernet port.
Run a cable from each computer to the modem. One end should go in the computer and the other end of the cable will go into one of the two ports of the splitter. You'll need to use phone cables with a dial-up modem and Ethernet cables with a cable or DSL modem.
Link the cable modem to a wireless router if you'd like to use a wireless connection. Plug one end of the cable into the Ethernet port on the back of the modem and plug the other end into the port on the wireless router. Notably, some models serve as both a modem and router; for these, you will not need a separate wireless router.
Plug a wireless receiver into each computer's Ethernet port. For newer PC computers and most Macs, this step is not necessary since the wireless receiver is built-in, so an external receiver is not required. A review of your computer's manual will reveal whether the computer has an internal wireless receiver.
Turn on the modem and the router and allow them to start up. The on/off buttons are usually located on the back. If there are lights present, they usually turn green when start-up is complete.
Configure your wireless network. The method used to configure the wireless network varies dramatically depending on your computer, the operating system and the router. All routers come with detailed directions on how to configure the wireless network on Macs, PCs and the various operating systems that are used for each. Some computers, like Macs, feature a largely automated configuration process when used with the Mac AirPort router.
Connect to the wireless network with each computer. Most newer computers will do this automatically when you open a web browser program; other computers may require a manual process whereby you must connect to the wireless network before you can go online.
Tips and Warnings
You can connect more than two computers to a wireless network.