I have the following domains:
I have been able to setup site1.com to point to my server and can access it with Remote Desktop. I want to add all of the other sites to access the same server.
I have already setup DNS records with CPanel and Domain Aliases. All of the name server records for these domains point to the NS of site1.com.
Not entirely sure what you are asking?
If you are asking in a Windows Server 2008 R2 server can join multiple Windows domains, then no.
If you want to have multiple websites on the same server, with different domains, all going to the same address, then this is done by having the DNS for the domains resolve to the same IP address.
It seems like you are asking a couple of questions which is typically not recommended. If you have multiple questions split them out into multiple questions.
There are two things you have to modify to get multiple domain names to point to a single site/IP on your web server.
Check out the IIS site to learn how to setup a web site. You can follow the instructions to setup host headers for each of your domains site2.com, etc.
For each domain you should be able to specify an A record that then points to the IP address of your server. Once completed it should then browse to the same site as site1.com.
