Im using windows 2000 Server, and I need to forward all the requests to the
example.com site to another DNS Server. How do I do this?
As JdeBP states, What you are asking for is a conditional forward to aaa.com. I.E. Requests sent to your DNS server for aaa.com are sent to the specified DNS server.
If your DNS server is Windows Server 2000 then you can't setup a Conditional forward. Your only option would be to set the DNS server you want to use to resolve aaa.com as a regular forwarder. Or you could upgrade your DNS server to Windows Server 2003 or higher, which support conditional forwards.
You don't. Upgrade to Windows Server 2003 which supports conditional forwarding.
The best way to do that is with your registrar rather than the current DNS servers. Update your registrar to point directly to the new DNS servers.
A 2nd level domain is not meant to be redirected so Windows 2000 DNS server doesn't support this (I doubt that DNS supports that).
If you explain further what you intentions, we can consider other creative ways to achieve your goals.