Grumpy's suggestion is good, but keep in mind if you have any issues with your connections, and you are using your own modem and router, they won't support you very well and will most likely blame any issues on your equipment which you are now responsible to replace.
I recently learned from Radio Shack that this a is wireless router-modem combo. I think it's Charter's way of keeping you paying for something you don't want to bother trying to figure out a way to replace it. I can hook up a cable modem purchased from Wal-Mart and run an ethernet wire from it to one computer and a USB cable to the other computer. That will solve my problem. Thank you very much!
If you connect your computers right to the modem without a router/firewall in between, make sure you install some type of Firewall software on the computers. Or at least enable the built-in Windows Firewall. Having computers hanging off the modem directly is not very safe, the risk of a random hacking scan hitting your computers is hugely increased.