Disable IPv6 In Vista
Windows Vista contains both the familiar IPv4 stack and the new IPv6 stack.
IPv6, when it's rolled out across the Internet over the next few years, will bring an end to the problem of running out of IP addresses and improve other aspects of TCP/IP operation.
However you do not need IPv6 at present time disable IPv6 on the Windows Vista system.
Check this site on how to disable IPv6