Yes, it can be a good plan.
1. Run DNS on stand alone win 2003, and you can transfer zones from your
existing DNS, by first creating secondary zones and after replication
promoting them to primary zones.
2. Point the Win 2003 server to itself for DNS, and in the DNS server use
forwarder for internet resolution.
3. Then point the clients to win 2003 DNS.
Do not point any machine to ISP's DNS server, even as alternate DNS, only
point to win 2003 DNS.
When you are ready for promoting win 2003 to an AD,
in the DNS first add a primary forward lookup zone giving the fqdn of the
planned domain name. Allow dynamic updates for this zone and then run
dcpromo.
be
new