Hello guys,
Even i had the error on my activation of windows 7 ultimate edition, the simple workaround is to go login to your Router login url
http://192.168.1.1/ (URL changes depend upon router manufacture)
login with username: admin password: password or admin
then go and disable DHCP once done click save and reboot your Modem. Once done re-try windows activation this would work perfectly.
What happens when you buy OS which has "activation on geographic locations" Microsoft check's with your ISP info, if your DHCP is on then it gives you IP as 192.168.1.3 something like that and Microsoft using that IP can't fetch your ISP details.
Regards,
ZAK
iLoVeUzAk ~ oFfIcIaL wEb sItE