I know we all do this (disable ipv6 because we're generally not using it internally in Windows domain environments) and oldskools's answer is just about the best way to do this but there are some words of caution that should be pointed out.
Microsoft test everything with ipv6 enabled and do not test current generation OS's (Vista, 7, W2K8/R2) with it disabled. So far this has never been a major issue for me but I have come across situations where this has caused problems (Exchange 2007 to 2010 upgrade). The reason that there is no longer a simple option e.g. (netsh ipv6 disable) to do this is that Microsoft would prefer it if we didn't do this.
Disabling ipv6 (or ipv4 for that matter) after you have installed the DNS server role on a server you will experience timeouts.
Even without ipv6 enabled you may find that some ipv6 activity (DNS again) is going on and if your DNS server is returning answers to AAAA requests then there may be additional name resolution traffic, and possibly requester side timeouts, while they are being dealt with.
This Technet Blog article expands on this, and specifically mentions that Microsoft's Common Engineering Criteria require ipv6 support to be enabled. At some point enabling ipv6 will be required and since there is no simple way (ie by GPO) to do this globally we're all looking at creating some work for ourselves in the future when we are forced to (re)enable it in order to remain supported by Microsoft.