My first question is are you using wireless router or hardwired ethernet connection. If wireless try resetting router depending on when it was purchased you may have to install new firmware drivers. If not and you are hardwired do network diagnostic and use device manager to see if network card is listed. If it is try doing a last known good config possible you have some corruption in in network/lan drivers.turn system off wait 20-30 sec turn back on hit f2 key or f8 key on some models arrow down to last know hit enter pick a day before you last used 4 months prior to last use enter and let system reboot. If you are still unable to connect to net network card could be damage from possible moisture and or dust, or even static electricity from being store in none air tight sealed container. Have it replaced or you can purchase a USB powered nic( network adpater)card at local Walmart, Radioshack, or I would go to a BestBuy or CompUSA store to purchase one.