How do I prevent one IP from creating a DNS entry on a multi-homed server?
If both ip addresses are bound to the same network card then you won't be able to use the solution Zoredache provided... exactly. What you can do is follow his suggestion and then create a static A record for the ip address that you do want registered in DNS.
Are the multiple addresses assigned to a single adapter, or do you have have multiple adapters.
If you have multiple adapters then you should be able to un-check the 'Register this connection's addresses in DNS' box. See http://support.microsoft.com/kb/305553#6