I can connect to my wireless router, which I know is connected to the internet (because I've tried with an ethernet cord), but my laptop won't access the Internet. I can't browse WEB pages nor use AIM. What should I do?

I'm using: Windows XP Home; it is up to date.
Avast 4.7 Home Edition.
I have ran Spybot, Adaware, and Ewido Antimalware, and Avast! Antivirus on reboot.. I tried disabling Avast! to see if that was a PROBLEM but nothing changed.
I use Windows FIREWALL, and avast! is listed as an exception.
No other antivirus software being used.
Note- I can access the Internet via ethernet cable, just not wireless.Did this ever WORK? If so, what has changed? What hardware is involved?
Yes, it worked. I don't know what changed. Atheros wireless network adapter and a Trendnet router are involved. The router definetly still works cuz I can connect to it with another computer and access the Internet. I think there's just some setting or something on my laptop that prevents it from accessing the internet even though I am definetly connected.Go to start/run, type in command, and click OK. In the command prompt box type ipconfig and press enter. What is shown as the IP address?So I RESET my router and that solved the problem. Embarrasing.
Thanks for the help.