Networking your Internet
Networking can be done with Cable broadband and with the USB modem but it is difficult.
If you have ADSL broadband and you are using the Ethernet connection with your modem, the answer is simple.
For ADSL networking, obtain an Ethernet Networking switch. The switch (also called a hub and a router) comes in various port numbers. You need a switch with at least one plus the number of computers to be networked. I suggest a 4 port switch, unless you have more than 3 computers to network (8 port and 16 port are available but for one ADSL connection, 8 PCs would be asking a lot).
So, a 4 or 5 port Ethernet switch/router suits most homes – costs $60 or so.
Your ADSL is working with one computer so it will work quite well with two or three others, providing the others have the necessary configuration.
Any computer to be added to the network must have a network card – most modern computers and laptops have the card as standard.
TCP/IP must be installed – if you have Windows XP you should be OK.
Cables must run from each PC to the switch and a cable from the switch to the router. You can buy these ready made.
Turn everything on and at least the original PC should work without fuss.
If the extra computer/s work, great! Now you can turn on Sharing and then you can share folders on one PC with the other computers.
The extra computers may need a tweak or two. You may need to turn on networking and other things may need configuring, but try it and see.
Ask for help if it gets too hard.