I can access the router but not the internet

Try 'repairing' the connection. On Windows XP its the little computer icon with waves coming out of it - likely in the lower right system tray. Right-click on it and select 'repair'.

Please post an update if that solves the problem.

go to start menu then type in run "ping yahoo.com -t"

If you get reply then your ip addreses is ok.
then you need to restart your dns service of computer.
For that go to start menu then type in run "services.msc"
then you see in right side "DNS CLIENT"
right click on it and stop then restart it again same way.
then restart computer then check.
If problem still arise then check ip sub net and gateway of other computer on which your working fine then set ip address again
Thanks for using fixya.