"My computer keeps showing me an error saying another computer has the same IP address. I'm not sure what an IP address is or why another computer has the same IP. What does that mean?"
An IP address is what your computer uses to identify itself to other computers, game consoles, and the router or modem on your home network. Typically, the cable modem or DSL router in your house will automatically assign an IP address to each computer or networked device in the house. When two different devices get the same IP address, it can cause communication problems on your home network. Both Windows and Mac OS X automatically detect other devices connected on your home network and will give you a warning like the one you are seeing when more than one computer is using the same IP address. To fix the error and prevent issues on your home network, you need to make a couple of changes.
Since there are multiple devices on your home network, as evidenced by the duplicate IP address error, what you need to do is make sure you get your computer a different IP address from the router that is handing them out.
In order to do this, you are going to need to type in some commands using the command line window. To launch the command line window, either press and hold the Windows key while also tapping the R key, or click Start, then type cmd in the search box and hit enter (on Windows XP type start and click Run).
The above step will bring up a black window with a flashing cursor next to your username. Type ipconfig /release and the hit the enter key. You will see a bunch of text scroll by quickly and it will return you to the flashing cursor. This process removes the IP address your computer is currently using.
Next, you need to have your computer tell the router it wants a new IP address. This requires typing ipconfig /renew and hitting enter again. You should now have a different IP address and the same IP address error will be resolved.
If for some reason that did not solve the problem, type ipconfig /release and then hit enter one more time. After that, restart your computer and it will get a new IP address when the computer completes restarting.
There is one other possibility, which is that your router or modem is having a problem in correctly assigning IP addresses. The fix for this is generally to unplug your router or modem, leave them unplugged for about 10 seconds, then plug the router or modem back in so that it can power back up. When the router or modem completes a restart, it will need to reconnect to all the computers and devices in your house and reassign IP addresses.