Unable to change the workgroup of the server to domain name

I am unable to change the workgroup of the server to my domain name on the DC

The following is the error i get...

Note: This information is intended for a network administrator. If you are not your network's administrator, notify the administrator that you received this information, which has been recorded in the file C:\Windows\debug\dcdiag.txt.

The following error occurred when DNS was queried for the service location (SRV) resource record used to locate an Active Directory Domain Controller (AD DC) for domain "core.com":

The error was: "DNS name does not exist." (error code 0x0000232B RCODE_NAME_ERROR)

The query was for the SRV record for _ldap._tcp.dc._msdcs.core.com

Common causes of this error include the following:

• The DNS SRV records required to locate a AD DC for the domain are not registered in DNS. These records are registered with a DNS server automatically when a AD DC is added to a domain. They are updated by the AD DC at set intervals. This computer is configured to use DNS servers with the following IP addresses:

127.0.0.1
76.12.70.126

• One or more of the following zones do not include delegation to its child zone:

core.com
com
. (the root zone)

I have entered made the DC as the prefered DNS server by entering its IP address on its NIC

C:\Users\Brett>ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : 202668-9
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection
   Physical Address. . . . . . . . . : 00-50-56-A0-22-50
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 76.12.48.X(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.248
   IPv4 Address. . . . . . . . . . . : 76.12.48.100(Preferred)--set by me-->load balancing
   Subnet Mask . . . . . . . . . . . : 255.255.255.248
   Default Gateway . . . . . . . . . : 76.12.48.X
   DNS Servers . . . . . . . . . . . : 76.12.70.126 -->DC's IP address
                                       127.0.0.1
   NetBIOS over Tcpip. . . . . . . . : Enabled

Could you tell me what the problem could be?

Further logs from my investigation

C:\Users\Brett>nslookup core.com
Server:  UnKnown
Address:  76.12.70.126
Name:    core.com

C:\Users\Brett>nslookup
Default Server:  UnKnown
Address:  76.12.70.126

set q=srv
_ldap._tcp.dc._msdcs.core.com
Server:  UnKnown
Address:  76.12.70.126

*** UnKnown can't find _ldap._tcp.dc._msdcs.core.com: Non-existent domain

C:\Users\Brett>dcdiag

Directory Server Diagnosis

Performing initial setup:
   Trying to find home server...
   ***Error: 202668-9 is not a Directory Server.  Must specify /s:<DirectoryServer> or  /n:<Naming Context> or nothing to use the local machine.
   ERROR: Could not find home server.

P.S: The Active Directory Domain services on the server is stopped and i am also unable to start it.

I am into programming, this is my first attempt at any such task. I hope to find some useful answers

That's not how you load balance Remote Desktop services. There's a dedicated Windows Server role for that specific task: Remote Desktop Gateway