Check your IPv4 settings in Win7. Could be a dns issue, timing out if it is set for a slow or very remote location.
Do a trace route to google and see where is bottlenecks:
press start, type in cmd, type in tracert 74.125.4.100(one of google's ip's). The result will show you the route that the data is traveling through the internet and if there is something along the way slowing you down, you will be able to see. Then go try it in XP see if the times and routes are the same in tracert.
Also, go to the command line, type in ping google.com, then ping the ip address that shows up, if the ping is alot faster when you ping the ip and not the name then its definitly a dns issue