i installed vista and installed my adsl modem and configured my modem and all steps just like i did in my xp.
my adsl modem software shows that modem is responding and working properly and sending/recieving packets but in my network center it says that my network is unidentified and connection to internet is disabled or something.simply i cant connect anywhere on web.
i disabled my lan connection so theres only one connection(adsl) is enable and running.
any idea whats the cause?

Try this; Create another connection after disabling the exisiting one, but this time choose to make the connection 'Public', then delect the previous disabled connection and don't disable any lan connection. Then see what happens, if you can connect to the internet then.