Does anyone know how to cleanup DNS records?

I have a quite a list of old host names in the DNS server database that
don't have IP addresses associated with them. How do I get rid of them
without deleting them one by one?

Also, is there a way to cleanup the DHCP address assignments? I have several
types of assignment to get rid of including:

Excluded due to unauthorized error messages
Dynamic addresses that have expired

Any help with this would be appreciated.

Tech Support
Dinwiddie County Public School