You can't have two people using one computer at the same time, either physically or remotely.
It's called a Terminal Server not a DNS Server.
Terminal server is designed to give access to multiple remote users. You can modify Windows 7 to allow multiple users. Technically, however, you should be using a Terminal Server like Server 2008R2 or Multipoint Server. Here's an example:
https://www.youtube.com/watch?v=l4bAlp52z1A
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