I have www.mydomain.com hosted elsewhere. I have the registrar point mysubdomain.mydomain.com point to Windows2008 r2 a completely different server. I go to edit bindings for the site add mysubdomain.mydomain.com but it never works bringing up the site.
Is your registrar the DNS host? You must also make sure it created an A-record for the subdomain to point to your Win2008R2 server. Try to ping your subdomain and see where it resolves. If the ip address resolves to something else than your Win2008 server, then it's a DNS misconfiguration. If the IP address is your Win2008 server, then it's a configuration problem on IIS.