Vista - Cannot get internet on laptop anymore

alright, so this past friday i went to go turn on my hp compaq presario laptop running vista and once it booted up, it said that i was connected with limited connectivity or to my d-link wireless router, i restarted and the same thing happened. sometimes it says that it is connected to an unidentified netowrk instead. so i started to mess around with my router but my other computer was connecting fine. I then tried to connect via ethernet straight from my modem and it was still the same case. i have even brought the laptop over to my buddies but it says the same thing over there too. it is obviously a problem with vista but i have no clue what it is or how to fix it. i have been looking all over the internet for solutions but nothing has worked so far. any help will be greatly appreciated.