Network issue

OK, I got a really helpful response last time I had a question here. Trying again - got a network question I can't resolve.

I've got a wireless network set up here in the house. (Had, anyway.) The desktop computer, with Vista installed, is hardwired to the network router with ethernet cable; the laptop has a built-in wireless adapter and the Tivo has a wireless adapter hooked up. Here's what I can't figure out:

When I click Network off the Start menu (on the desktop), the only device that shows up is the PC itself. The router used to appear there; it does not any more. Neither does the laptop or the Tivo, both of which used to. I have gone to the Network and Sharing Center under Control Panel and made sure Network Discovery is turned on - even flipped it on and off - but this does not work. I have also tried setting up the network again, only to receive the following error message:

"Windows did not detect any wireless network hardware.

If you have a router, make sure it is plugged into this computer and try again. Check the information that came with the router for more detailed instructions. "

(Admittedly I have not done that last part.)

Here's the catch - the peripheral devices (laptop and Tivo) do see the network, and connect to it. However they cannot connect to the Internet through it, and do not show up when I try to view computers and devices. Obviously, the desktop has no problem connecting to the 'Net through this router. It is not connected to the cable modem except through this router. On the laptop (running XP), however, I receive the following error message:

"Limited or no connectivity

You might not be able to access the Internet or some network resources. This problem occurred because the network did not assign a network address to the computer. "

It is, however, connected: when I "View wireless networks" it says "You are currently connected to his network." Signal strength is strong. The Tivo also sees this network but also cannot connect to the Internet through it.

I suspect I could fix this problem if I could get to the router homepage, which I used to be able to do. I no longer can, however, because of the router not showing up in the network display.

 

Connect the computer to the router using an Ethernet cable to access the router set up details. This is done by typing 192.168.n.n (n depends upon the make of router) into a browser address bar window. When asked for the username and password, type the default values for your router.