new DNS client scope subnet mask

How to I clear my dhcp to create a new cleent scope without the old stuff showing up? I’ve tried removing and readding the dhcp, editing the registry and everything else without fail. Someone mentioned a text file that needs to be cleared…. ????
Our provider has just changed our DNS and given us a new subnet of255.255.255.240 (?). When I go in and change the client scope (set of intranet IPs), the dhcp will NOT take the new sub. It keeps defaulting all the old stuff regardless if I delete everything including the dhcp.mdb. I can get everyting inside, but can’t get out. I haven’t gotten my NAT router yet, but according to Bluegrass I shouldn’t need it. It works if I go static, but we run dhcp.
Regards,
Lori David
FAST Software