Error while installing Exchange or any of its Service Packs - Setup encountered a problem while validating the state of Active Directory: could not find Active Directory site to shich this server belongs.

   
1) Open up AD Site and Services, you should see a container called Subnets.
2) Lets say you have a IP subnet 192.168.0.xxx, add this to the Subnets Container, might looks like 192.168.0.0/24.
3) Beside this you should see a site called Default-XXX something, add the subnet to this site and you are done.