You need to have your computer on the same subnet as the router.
The easiest way to do this is to use the reset button on the router (usually held in for 10-30 seconds until all lights flash, then release) to reset to factory default. Next, restart your computer so it will pick up an address from the router. (If you had put a static address on your computer, you will need to temporarily change it to automatic.)
Once the computer has its address, you can try to connect to 192.168.0.1 again.
If that still doesn't work, you need to find out what the router thinks it is by finding out the status of your computer. Go to START - RUN and type CMD. click "ok". This will bring up a command window, with a line something like this:
C:\Documents and Settings\name>
Type "ipconfig" and press ENTER to display the settings in your computer. You should see 192.168.y.x as the computer address and 192.168.y.1 for the gateway. (NOTE: y should be the same in both places!)
The gateway address is the address of your router, and that is what you should use to access (even if it isn't 192.168.0.1).