That's a puzzler... assuming your internet connection goes to your router first, and then to your computer, and you can use the internet fine it would seem that your router is working. And if ipconfig is telling you the right default gateway 192.168.0.1 then you should be able to access the router's web setup page...
But maybe the router doesn't want your computer to see it's setup page, if you're using wifi maybe the router is setup to not allow wifi users to see the setup, try connecting a physical network cable from the router to your computer and see if it works then.
Or maybe your router's web setup page is disabled or doesn't work, a very few routers (like DD-WRT/OpenWRT) might only allow access through telnet if the web setup is turned off, you could try (from a command prompt/cmd) "telnet 192.168.0.1" and if it asks to log in you might need a username like "admin" or "root" & password.
Or if the router is messed up maybe the web setup just won't work... unplug it for a few minutes & plug it back in maybe, or try the reset button, but if the internet's working ok now I don't really want to reset it, then you'd have to set up the wireless name & password & security type, and any other open ports or time or mac filters, etc... may need to know the default password too.
Can also try, from a command prompt/cmd, "ping 192.168.0.1" and see if the router replies, but the router could be set to ignore pings too, especially from wifi. If you've got a traceroute program (maybe tracert, I don't know what your windows would have) you could traceroute www.yahoo.com and that should show you most of the computers "in between" you and www.yahoo.com, the first or second result should be your router 192.168.0.1, followed by maybe the cable/dsl modem and then some of your isp's computers. That would at least confirm the router (gateway) address...
One other thing, make sure the web browser isn't using a funny proxy or has other weird "internet connection" settings, it should be set to "direct internet connection" or similar.