well, if you have your domain name with godaddy.com do these steps to change nameserver:
* login to your account at godaddy.com
* Once you are logged in, click on the
My Account link
* Now find the link that says:
Manage Domains
* in the Domain Name Control Center, click on the domain name you want to make the changes to
* Your domain name current setting will show, look for where it says
Name Servers: if those nameserver are not the one you want, then to change them click on the icon where is says
Nameservers the icon will look like this:
* Chane the nameserver to the new namerserver you want, in your example, you should have ns1.old.com and ns2.old.com so just change them to ns1.new.com and ns2.new.com
changes will take about 48 hours to complete throughout the world servers.