Unable to setup Wireless Router

[scissorcrow]

This morning I awoke to find all the lights on the router off. My mum says the internet was fine earlier.
We tried a few things and in the end got a new power adaptor, lights back on.

We're using a Cisco Router 800 series and an Aironet 1110 Wireless Access Point.

My laptop wouldn't connect wirelessly so I put the ethernet from the WAP into the laptop and it worked. I then searched how to setup the wireless connectivity as I have not done this before, I followed instructions of typing ipconfig into command prompt to find the default gateway ip, however when I type this into the address bar of Safari, FireFox and IE they all just say 'Cannot connect to server'

I have tried typing the ip address into the address bar a few months previously and nothing happened then either.

As a side note we tried putting the ethernet cable into my mums PC and it freezes on startup. If we put the cable in after it's all loaded it freezes. I suspect there may be malware or the ethernet driver is out of date, but without internet am unable to fix those issues?

A neighbour who has since moved set the network up, does it matter which computer we access the router through? My mum keeps saying it's to do with the home group but I have not heard of this before.

Thanks

EDIT
When I ping 192.168.0.1 (the default gateway) I get a reply

[CimmerianX]

Home group is Microsoft's way of sharing files in a home network. Not involved here.

When you ping 192.168.0.1, are you wired or wireless?

Can you ping beyond the gateway? Ping 4.2.2.1 or ping 8.8.8.8. Do you get a response. If yes, then your basic connectivity is ok. Now ping www.google.com. you should see it attempt to ping an IP address. If you get no ip address then dns is down. Check your dns settings.

[rubberman]

You may need to reset the router to factory settings - there should be a reset button (possibly recessed - needing a small device such as a pin to depress) on the back of the router that when held in for 10 seconds or so will reset it to factory settings. Then, you can use the default http address, admin id, and password to get into it from your computer and then reconfigure it appropriately. NEVER let a neighbor configure your network for you! Take control yourself!