The modem will provide internet to the main computer, but not to the other computer or my xbox. I dont understand why

The router is provided by your internet provider some companys only have modems which means you would have to plug your Xbox into the modem whith a Ethernet cable call your provider to make sure the router has WiFi if so just go to settings on Xbox and conne

If its not a black xbox 360 slim than it doesnt have wirless so you either need a wireless adapter or ethernet cord that will hook up to the modem from the xbox.

if you keep getting disconnected then i would do internet test,if theirs no fault your end then i would contact your internet provider,because has long has its not xbox live which i dont think it his then i would ring your internet provider,also let us no more details has in does your internet go down or just xbox live? does your router or modem light go off every 20 mins then quickly come back on?

So, you're saying that before two weeks ago, you did not have this problem? If that's the case, and it used to work, I'd call the ISP for you internet, and tell them what's happening, it's possible that the route may have developed issues, and they can check to see if there's something wrong on the internet connection that's causign the problem. It's also possible that Live has contracted too many new subscribers, and in your area they've overbooked the number of available connections and are having what I call "growing pains". If it's XBox Live's issue, it can take anywhere from a few weeks to months to get enough bandwith and authentication servers up to support the increase in customers. You could try a support call to XBOX Live to see if they are having issue (most companies *won't* admit this, but some are learning that people are very understanding and will admit when it's their issue.) So, especially if you're not getting dumped on any other service (like Netflix, or Hulu, or some such service), then either the teleco/ISP can help, or LIve can help; I'd try both; but, really it will probably be just a waiting game.

If you are having issues with other providers, you'd need to call the teleco, and set up a service call to do some signal analysis on your line, in case there's a crack in the line to the service box between your home and the what's called the teleco's HOME OFFICE, the green box down the street from your home. If a line is cracked, it could be corroded. One way to know this, is that this issue gets worse right after heavy storms, and the ground gets soggy from the rain, which interferes with the signal. Hope this helps.

I am not that much clear whether you can change your Ip adress, but any queries regarding Ip-detais can be solved here, http://www.ip-details.com/

Do you have a router? Most cable/DSL modems have built in routers (more than one ethernet port). The ethernet cable looks like a large phone cable (it's called RJ-45). If so, you will need to powercycle your modem.

You can powercycle your cable modem by:

Unplug the power from your modem for 1 minute (no lights on the device). Plug it back in, and reboot both devices and they will both have IP address to get out to the internet.

Let me know how it goes or if you have anymore questions.

Is the main computer connected to the router or to the internet directly? If it is a cable modem for the internet, make sure you turn that off, as well as the router, and connect the cable modem to WAN on the router and put the modem on first, then the router. Connect the computers, xbox, etc to the router

if you dont have a router, you can either have the xbox or the pc conneted to the internet, not both. you have to have an eithernet cord or a usb 2.0 high speed usb chord that goes directly from the xbox to the modem. you cannot go from the modem to the computer then to the xbox.

First you need to figure out if the issue is with your router, your modem or xbox. Does the issue occur if you connect directly to the modem? If so, look into the rooter. If you have the same issue with the modem, try connecting a PC and see if the connection also drops. If that's the case, your modem is the issue. Call your internet provider and they should provide you with a new one. If you xbox is the problem then bring it to a repair shop explaining the issue.

I would suggest that if you are xbox live unless you have fast internet dont use the internet for other things like your computer. Its most likely that there is not enough bandwidth for everything. If that doesnt work call you internet service provider and explain the problem to them and if they are a legitamate company they will help you out.