HELP! Windows 7 laptop no internet access

I have a Windows 7 HP laptop. The problem is that i can connect to the network but, i don't have internet access. There are 2 other laptops in the house an XP and Vista that don't have issues connecting. I thought it was a problem with the laptop itself. I sent it to HP to get it looked at and they fixed what seemed to be the problem. However, i got the computer back and it still has the issue. If i troubleshoot it the message says "Default Gateway is unavailable" once i close the box and troubleshoot again i have internet. Once i have internet about 15-20 minutes goes by, i don't have internet and have to start the process all over again. I don't know anything about the computer like i have read in other forums. I will have to be walked through fixing this step by step (in dumb terms)!!? Can someone please help! You can email me at mickeymouse90082012@gmail.com

Source: http://social.technet.microsoft.com/Forums/en/w7itpronetworking/thread/ceb9b8cb-2405-4301-9e44-6aada07b3dc3

sodastream dan marino godaddy did the groundhog see his shadow Ray Lewis Murder UFC 156 my bloody valentine