cant connect to local area connection on home network? windows 7?

I have an hp computer desktop with windows 7 (x86) and it is connected to a linksys router via an ethernet cable that is connected to a modem...for over a year the internet and everything else has worked fine...nothing new installed..last week i was on the net and all of a suddent the connection went off...i didnt install anything new or change settings...in network and sharing center it says...unidentified network public network no internet access..and there is a yellow triangle with ! on the bottom...also i have 2 laptops and a desktop that are wirelessly connected to the router and the internet on them works just fine...can you throw every possible solution at me...i have tried every suggestion i could find...from diabling and reenabling LAC adapter...disabling and updating LAN adapter...but nothing works...i unplugged my router and modem and shut down the computer..restarted everything but nothing...something interesting is that when i tried renewing my ipaddress via ipcong ..renew/release it saidmedia state disconnected...and renewed it but then syas an error occured...unable to contact DHCP server..also i am 100% sure my ethernet cable is fine b/c its connected and i tried it on another laptop with the same router and it worked flawlessly ..plz help..