DNS problem with PPTP

I have two subnet connected with two mikrotik routers.
The first router is directly connected to the Internet while the second router is connected to the first router.
I have my a local DNS server with Active directory integrated zone which is also my DNS server. My DNS server is also pointing to Godaddy .com. I can see all the computers on this subnet 192.168.1.1 registered to the DNS Sever, this is where DNS Server reside but the second subnet which is 192.168.2.1 is not registering to on DNS server. You can join computers to the Domain without an issue from this 192.168.2.1 subnet also you ping any computer with its name from any subnet. You can not ping any computer with its name from from Mikrotik router but ping from PC is ok.

How can I make all the computers from different subnet to register on the DNS Server?
How Can I make Mikrotik routers to ping all the computers on the network without registering the hosts on mikrotik routers?

My second problem is I configured PPTP on Mikrotik router with radius authentication with Windows2008. Users can logon perfectly. Proxy-arp is enabled on very subnet. I can ping the computers with its IP address from any subnet. I cannot ping computers with its name and I can not browse computers resources on the network.
When I logon from PPTP client and I ping my domain with its name and it gives me the public IP address instead of private IP address. Is it because my domain is pointing to Godaddy.com? I can also ping the domain with its private IP address.

How Can I fix this DNS problem?
How can I make all users to browser all the resources on the network?
How can I make PPTP clients to ping the domain with its name and get private IP address?

Thanks in advance.